HNF4A is essential for specification of hepatic progenitors from human pluripotent stem cells.

The availability of pluripotent stem cells offers the possibility of using such cells to model hepatic disease and development. With this in mind, we previously established a protocol that facilitates the differentiation of both human embryonic stem cells and induced pluripotent stem cells into cells that share many characteristics with hepatocytes. The use of highly defined culture conditions and the avoidance of feeder cells or embryoid bodies allowed synchronous and reproducible differentiation to occur. The differentiation towards a hepatocyte-like fate appeared to recapitulate many of the developmental stages normally associated with the formation of hepatocytes in vivo. In the current study, we addressed the feasibility of using human pluripotent stem cells to probe the molecular mechanisms underlying human hepatocyte differentiation. We demonstrate (1) that human embryonic stem cells express a number of mRNAs that characterize each stage in the differentiation process, (2) that gene expression can be efficiently depleted throughout the differentiation time course using shRNAs expressed from lentiviruses and (3) that the nuclear hormone receptor HNF4A is essential for specification of human hepatic progenitor cells by establishing the expression of the network of transcription factors that controls the onset of hepatocyte cell fate.

A cell surfaceome map for immunophenotyping and sorting pluripotent stem cells.

Induction of a pluripotent state in somatic cells through nuclear reprogramming has ushered in a new era of regenerative medicine. Heterogeneity and varied differentiation potentials among induced pluripotent stem cell (iPSC) lines are, however, complicating factors that limit their usefulness for disease modeling, drug discovery, and patient therapies. Thus, there is an urgent need to develop nonmutagenic rapid throughput methods capable of distinguishing among putative iPSC lines of variable quality. To address this issue, we have applied a highly specific chemoproteomic targeting strategy for de novo discovery of cell surface N-glycoproteins to increase the knowledge-base of surface exposed proteins and accessible epitopes of pluripotent stem cells. We report the identification of 500 cell surface proteins on four embryonic stem cell and iPSCs lines and demonstrate the biological significance of this resource on mouse fibroblasts containing an oct4-GFP expression cassette that is active in reprogrammed cells. These results together with immunophenotyping, cell sorting, and functional analyses demonstrate that these newly identified surface marker panels are useful for isolating iPSCs from heterogeneous reprogrammed cultures and for isolating functionally distinct stem cell subpopulations.

JD induced pluripotent stem cell-derived hepatocytes faithfully recapitulate the pathophysiology of familial hypercholesterolemia.

UNLABELLED: Elevated levels of low-density lipoprotein cholesterol (LDL-C) in plasma are a major contributor to cardiovascular disease, which is the leading cause of death worldwide. Genome-wide association studies (GWAS) have identified 95 loci that associate with control of lipid/cholesterol metabolism. Although GWAS results are highly provocative, direct analyses of the contribution of specific allelic variations in regulating LDL-C has been challenging due to the difficulty in accessing appropriate cells from affected patients. The primary cell type responsible for controlling cholesterol and lipid flux is the hepatocyte. Recently, we have shown that cells with hepatocyte characteristics can be generated from human induced pluripotent stem cells (iPSCs). This finding raises the possibility of using patient-specific iPSC-derived hepatocytes to study the functional contribution of GWAS loci in regulating lipid metabolism. To test the validity of this approach, we produced iPSCs from JD a patient with mutations in the low-density lipoprotein receptor (LDLR) gene that result in familial hypercholesterolemia (FH). We demonstrate that (1) hepatocytes can be efficiently generated from FH iPSCs; (2) in contrast to control cells, FH iPSC-derived hepatocytes are deficient in LDL-C uptake; (3) control but not FH iPSC-derived hepatocytes increase LDL uptake in response to lovastatin; and (4) FH iPSC-derived hepatocytes display a marked elevation in secretion of lipidated apolipoprotein B-100. CONCLUSION: Cumulatively, these findings demonstrate that FH iPSC-derived hepatocytes recapitulate the complex pathophysiology of FH in culture. These results also establish that patient-specific iPSC-derived hepatocytes could be used to definitively determine the functional contribution of allelic variation in regulating lipid and cholesterol metabolism and could potentially provide a platform for the identification of novel treatments of cardiovascular disease. (HEPATOLOGY 2012).

Targeting Ribonucleotide Reductase Induces Synthetic Lethality in PP2A-Deficient Uterine Serous Carcinoma.

Uterine serous carcinoma (USC) is a highly aggressive endometrial cancer subtype with limited therapeutic options and a lack of targeted therapies. While mutations to PPP2R1A, which encodes the predominant protein phosphatase 2A (PP2A) scaffolding protein Aα, occur in 30% to 40% of USC cases, the clinical actionability of these mutations has not been studied. Using a high-throughput screening approach, we showed that mutations in Aα results in synthetic lethality following treatment with inhibitors of ribonucleotide reductase (RNR). In vivo, multiple models of Aα mutant uterine serous tumors were sensitive to clofarabine, an RNR inhibitor (RNRi). Aα-mutant cells displayed impaired checkpoint signaling upon RNRi treatment and subsequently accumulated more DNA damage than wild-type (WT) cells. Consistently, inhibition of PP2A activity using LB-100, a catalytic inhibitor, sensitized WT USC cells to RNRi. Analysis of The Cancer Genome Atlas data indicated that inactivation of PP2A, through loss of PP2A subunit expression, was prevalent in USC, with 88% of patients with USC harboring loss of at least one PP2A gene. In contrast, loss of PP2A subunit expression was rare in uterine endometrioid carcinomas. While RNRi are not routinely used for uterine cancers, a retrospective analysis of patients treated with gemcitabine as a second- or later-line therapy revealed a trend for improved outcomes in patients with USC treated with RNRi gemcitabine compared with patients with endometrioid histology. Overall, our data provide experimental evidence to support the use of ribonucleotide reductase inhibitors for the treatment of USC. SIGNIFICANCE: A drug repurposing screen identifies synthetic lethal interactions in PP2A-deficient uterine serous carcinoma, providing potential therapeutic avenues for treating this deadly endometrial cancer.

Highly efficient generation of human hepatocyte-like cells from induced pluripotent stem cells.

UNLABELLED: There exists a worldwide shortage of donor livers available for orthotropic liver transplantation and hepatocyte transplantation therapies. In addition to their therapeutic potential, primary human hepatocytes facilitate the study of molecular and genetic aspects of human hepatic disease and development and provide a platform for drug toxicity screens and identification of novel pharmaceuticals with potential to treat a wide array of metabolic diseases. The demand for human hepatocytes, therefore, heavily outweighs their availability. As an alternative to using donor livers as a source of primary hepatocytes, we explored the possibility of generating patient-specific human hepatocytes from induced pluripotent stem (iPS) cells. CONCLUSION: We demonstrate that mouse iPS cells retain full potential for fetal liver development and describe a procedure that facilitates the efficient generation of highly differentiated human hepatocyte-like cells from iPS cells that display key liver functions and can integrate into the hepatic parenchyma in vivo.

Generation of human induced pluripotent stem cells by simple transient transfection of plasmid DNA encoding reprogramming factors.

BACKGROUND: The use of lentiviruses to reprogram human somatic cells into induced pluripotent stem (iPS) cells could limit their therapeutic usefulness due to the integration of viral DNA sequences into the genome of the recipient cell. Recent work has demonstrated that human iPS cells can be generated using episomal plasmids, excisable transposons, adeno or sendai viruses, mRNA, or recombinant proteins. While these approaches offer an advance, the protocols have some drawbacks. Commonly the procedures require either subcloning to identify human iPS cells that are free of exogenous DNA, a knowledge of virology and safe handling procedures, or a detailed understanding of protein biochemistry. RESULTS: Here we report a simple approach that facilitates the reprogramming of human somatic cells using standard techniques to transfect expression plasmids that encode OCT4, NANOG, SOX2, and LIN28 without the need for episomal stability or selection. The resulting human iPS cells are free of DNA integration, express pluripotent markers, and form teratomas in immunodeficient animals. These iPS cells were also able to undergo directed differentiation into hepatocyte-like and cardiac myocyte-like cells in culture. CONCLUSIONS: Simple transient transfection of plasmid DNA encoding reprogramming factors is sufficient to generate human iPS cells from primary fibroblasts that are free of exogenous DNA integrations. This approach is highly accessible and could expand the use of iPS cells in the study of human disease and development.

The SRG rat, a Sprague-Dawley Rag2/Il2rg double-knockout validated for human tumor oncology studies.

We have created the immunodeficient SRG rat, a Sprague-Dawley Rag2/Il2rg double knockout that lacks mature B cells, T cells, and circulating NK cells. This model has been tested and validated for use in oncology (SRG OncoRat®). The SRG rat demonstrates efficient tumor take rates and growth kinetics with different human cancer cell lines and PDXs. Although multiple immunodeficient rodent strains are available, some important human cancer cell lines exhibit poor tumor growth and high variability in those models. The VCaP prostate cancer model is one such cell line that engrafts unreliably and grows irregularly in existing models but displays over 90% engraftment rate in the SRG rat with uniform growth kinetics. Since rats can support much larger tumors than mice, the SRG rat is an attractive host for PDX establishment. Surgically resected NSCLC tissue from nine patients were implanted in SRG rats, seven of which engrafted and grew for an overall success rate of 78%. These developed into a large tumor volume, over 20,000 mm3 in the first passage, which would provide an ample source of tissue for characterization and/or subsequent passage into NSG mice for drug efficacy studies. Molecular characterization and histological analyses were performed for three PDX lines and showed high concordance between passages 1, 2 and 3 (P1, P2, P3), and the original patient sample. Our data suggest the SRG OncoRat is a valuable tool for establishing PDX banks and thus serves as an alternative to current PDX mouse models hindered by low engraftment rates, slow tumor growth kinetics, and multiple passages to develop adequate tissue banks.

The clinical utility of screening of biochemical parameters in elite athletes: analysis of 100 cases.

OBJECTIVE: To determine the clinical utility of screening for biochemical parameters in elite athletes. DESIGN: A prospective sequential case series. SETTING: The Department of Sports Medicine at the Australian Institute of Sport. PARTICIPANTS: 100 elite athletes from 11 sports (56 male and 44 female athletes, mean age 19 years, range 16-27), undergoing routine medical screening. INTERVENTION: Initial and follow-up assessment of the following biochemical parameters in association with clinical assessment; serum iron, ferritin, transferrin, percent transferrin saturation, sodium, potassium, chloride, calcium, magnesium, phosphate, urate, urea and creatinine, total protein, albumin, creatine kinase (CK), lactate dehydrogenase, aspartate aminotransaminase (AST), alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, total bilirubin, cholesterol and triglycerides (non-fasting), and random glucose. RESULTS: 18 athletes showed no abnormalities on biochemical screening. 194 abnormal results were found in 82 athletes. 115 abnormalities were noted in 46 male and 79 in 36 female athletes. In 43 individual tests, the results did not return to normal on repeat testing. The most common abnormalities were increases in AST (27%), phosphate (13%), CK (13%), urea (12%) and bilirubin (12%). Three cases of hypercholesterolaemia and one case of haemochromatosis were identified, and one athlete, who was asymptomatic, was diagnosed with Epstein-Barr virus infection, which was suspected because of an abnormal liver function test. The other abnormalities found appeared not to be of clinical significance. CONCLUSION: Most abnormalities found on routine biochemical screening in elite athletes are of no clinical significance, therefore such testing should, if used only for clinical purposes, be abandoned. When athletes are tested for iron status it would be prudent to include assessment of serum cholesterol in those with a family history of hyperlipidaemia.

A "polypill" for acute tendon pain in athletes with tendinopathy?

Acute tendon pain in athletes is a condition that is difficult to manage. There are few treatment options that give adequate pain relief and have a theoretical basis for efficacy. We report the use of a novel "polypill" for tendon pain, and provide evidence for the basis for its use. We present it to stimulate discussion and research into a new area of tendinopathy.

A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction.

Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer systems produced by conventional sputtering methods have recently generated huge interest due to their applications in the field of spintronics. The sandwich structure with two correctly-chosen heavy metal layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Néel in character and with a fixed chirality. Lorentz transmission electron microscopy (TEM) is a high resolution method ideally suited to quantitatively image such chiral magnetic configurations. When allied with physical and chemical TEM analysis of both planar and cross-sectional samples, key length scales such as grain size and the chiral variation of the magnetisation variation have been identified and measured. We present data showing the importance of the grain size (mostly < 10 nm) measured from direct imaging and its potential role in describing observed behaviour of isolated skyrmions (diameter < 100 nm). In the latter the region in which the magnetization rotates is measured to be around 30 nm. Such quantitative information on the multiscale magnetisation variations in the system is key to understanding and exploiting the behaviour of skyrmions for future applications in information storage and logic devices.

Glutathione metabolism in type 2 diabetes and its relationship with microvascular complications and glycemia.

AIMS/HYPOTHESES: We hypothesized that there is decreased synthesis of glutathione (GSH) in type 2 diabetes (T2DM) especially in the presence of microvascular complications, and this is dependent on the degree of hyperglycemia. METHODS: In this case-control study, we recruited 16 patients with T2DM (7 without and 9 with microvascular complications), and 8 age- and sex-matched non-diabetic controls. We measured GSH synthesis rate using an infusion of [2H2]-glycine as isotopic tracer and collection of blood samples for liquid chromatography mass spectrometric analysis. RESULTS: Compared to the controls, T2DM patients had lower erythrocyte GSH concentrations (0.90 ± 0.42 vs. 0.35 ± 0.30 mmol/L; P = 0.001) and absolute synthesis rates (1.03 ± 0.55 vs. 0.50 ± 0.69 mmol/L/day; P = 0.01), but not fractional synthesis rates (114 ± 45 vs. 143 ± 82%/day; P = 0.07). The magnitudes of changes in patients with complications were greater for both GSH concentrations and absolute synthesis rates (P-values ≤ 0.01) compared to controls. There were no differences in GSH concentrations and synthesis rates between T2DM patients with and without complications (P-values > 0.1). Fasting glucose and HbA1c did not correlate with GSH concentration or synthesis rates (P-values > 0.17). CONCLUSIONS: Compared to non-diabetic controls, patients with T2DM have glutathione deficiency, especially if they have microvascular complications. This is probably due to reduced synthesis and increased irreversible utilization by non-glycemic mechanisms.

Sprague Dawley Rag2-Null Rats Created from Engineered Spermatogonial Stem Cells Are Immunodeficient and Permissive to Human Xenografts.

The rat is the preferred model for toxicology studies, and it offers distinctive advantages over the mouse as a preclinical research model including larger sample size collection, lower rates of drug clearance, and relative ease of surgical manipulation. An immunodeficient rat would allow for larger tumor size development, prolonged dosing and drug efficacy studies, and preliminary toxicologic testing and pharmacokinetic/pharmacodynamic studies in the same model animal. Here, we created an immunodeficient rat with a functional deletion of the Recombination Activating Gene 2 (Rag2) gene, using genetically modified spermatogonial stem cells (SSC). We targeted the Rag2 gene in rat SSCs with TALENs and transplanted these Rag2-deficient SSCs into sterile recipients. Offspring were genotyped, and a founder with a 27 bp deletion mutation was identified and bred to homozygosity to produce the Sprague-Dawley Rag2 - Rag2 tm1Hera (SDR) knockout rat. We demonstrated that SDR rat lacks mature B and T cells. Furthermore, the SDR rat model was permissive to growth of human glioblastoma cell line subcutaneously resulting in successful growth of tumors. In addition, a human KRAS-mutant non-small cell lung cancer cell line (H358), a patient-derived high-grade serous ovarian cancer cell line (OV81), and a patient-derived recurrent endometrial cancer cell line (OV185) were transplanted subcutaneously to test the ability of the SDR rat to accommodate human xenografts from multiple tissue types. All human cancer cell lines showed efficient tumor uptake and growth kinetics indicating that the SDR rat is a viable host for a range of xenograft studies. Mol Cancer Ther; 17(11); 2481-9. ©2018 AACR.

Blood tests in tired elite athletes: expectations of athletes, coaches and sport science/sports medicine staff.

BACKGROUND: The issue of the expectations of elite athletes, their coaches and non-medically qualified athlete support staff of consultations with sports physicians has not been previously dealt with in the sports medicine literature. As fulfillment of expectations of the content of a consultation may influence patient's satisfaction and clinical outcome, it is important to assess the expectations of athletes and, most importantly, coaches. OBJECTIVE: To assess the expectations and beliefs about fatigue, particularly in relation to blood tests, of athletes, their coaches and support staff in the specific context of tiredness of <7 days' duration. SUBJECTS: 28 senior sports science or non-medically qualified sports medicine staff, 22 elite coaches and 62 elite athletes from the Australian Institute of Sport were included in this study. METHODS: A single questionnaire. RESULTS: The expectation for a blood test at the initial consultation for short-term fatigue was particularly high among athletes (81%) and coaches (91%). This expectation increased in athletes if their performance was worsening. All groups unanimously suggested that a blood test be performed in cases of more prolonged fatigue. Increase in total training load was perceived to be the most important cause of fatigue, but issues relating to sleep were also thought to be highly relevant. All groups suggested that blood tests provide some degree of reassurance, and all groups suggested that the most important blood tests that might be performed related to exclusion of iron deficiency, anaemia and infection. CONCLUSION: Athletes and their coaches generally expect that blood tests will be performed even when fatigue has been present for <1 week. This is at odds with currently available evidence of the diagnostic utility of these tests. Despite the current evidence base, individual factors in the athletes, coaches and doctors need to be considered when deciding on whether such testing has to be performed.

Pinning and hysteresis in the field dependent diameter evolution of skyrmions in Pt/Co/Ir superlattice stacks.

We have imaged Néel skyrmion bubbles in perpendicularly magnetised polycrystalline multilayers patterned into 1 µm diameter dots, using scanning transmission x-ray microscopy. The skyrmion bubbles can be nucleated by the application of an external magnetic field and are stable at zero field with a diameter of 260 nm. Applying an out of plane field that opposes the magnetisation of the skyrmion bubble core moment applies pressure to the bubble and gradually compresses it to a diameter of approximately 100 nm. On removing the field the skyrmion bubble returns to its original diameter via a hysteretic pathway where most of the expansion occurs in a single abrupt step. This contradicts analytical models of homogeneous materials in which the skyrmion compression and expansion are reversible. Micromagnetic simulations incorporating disorder can explain this behaviour using an effective thickness modulation between 10 nm grains.

A Drug Screen using Human iPSC-Derived Hepatocyte-like Cells Reveals Cardiac Glycosides as a Potential Treatment for Hypercholesterolemia.

Efforts to identify pharmaceuticals to treat heritable metabolic liver diseases have been hampered by the lack of models. However, cells with hepatocyte characteristics can be produced from induced pluripotent stem cells (iPSCs). Here, we have used hepatocyte-like cells generated from homozygous familial hypercholesterolemia (hoFH) iPSCs to identify drugs that can potentially be repurposed to lower serum LDL-C. We found that cardiac glycosides reduce the production of apolipoprotein B (apoB) from human hepatocytes in culture and the serum of avatar mice harboring humanized livers. The drugs act by increasing the turnover of apoB protein. Analyses of patient medical records revealed that the treatment of patients with cardiac glycosides reduced serum LDL-C levels. These studies highlight the effectiveness of using iPSCs to screen for potential treatments for inborn errors of hepatic metabolism and suggest that cardiac glycosides could provide an approach for reducing hepatocyte production of apoB and treating hypercholesterolemia.

Clinical utility of blood tests in elite athletes with short term fatigue.

OBJECTIVE: To determine, in a population of elite athletes at their initial presentation with tiredness or fatigue, whether a set of haematological and biochemical investigations enhances the diagnostic process over and above the information gained from clinical history and examination. METHODS: A sequential series of 50 elite athletes were studied at the initial consultation for a primary complaint of fatigue, tiredness, or a synonym thereof. A standardised clinical history, physical examination, and series of haematological and biochemical test were performed. The effects of the results of the blood tests on the diagnosis made after the clinical history and examination were examined. RESULTS: In only one case did the test results lead to an alteration in diagnosis. Physical examination did not provide any findings that would not have been suspected from the history, except for a number of incidental findings not relevant to the presenting symptom. DISCUSSION: In cases of short term fatigue in elite athletes, a thorough clinical history is mandatory. Physical examination is unlikely to reveal any findings not suspected from the history. Routine ordering of a panel of blood tests at the initial consultation should be discouraged. Unless specifically indicated by the history and examination, investigations are not required at the initial consultation.

Optimising a curriculum for clinical haematology and biochemistry in sports medicine: a Delphi approach.

OBJECTIVES: To investigate issues of curriculum in the context of a postgraduate sports medicine training programme, specifically in the field of clinical biochemistry and haematology. METHODS: Following the Delphi methodology, a series of sequential questionnaires was administered to curriculum developers, clinical teachers, examiners, and registrars. RESULTS: Agreement on a core syllabus for this subject with an indication of the core aims and objectives of teaching and learning in this field and the associated required skills and competencies. An indication of current and ideal teaching and learning methods and reasons for these preferences. A consensus of key features of a teaching module for this field and of appropriate methods of examination. CONCLUSIONS: The data derived from this study, as well as the experience of engaging in it, will better inform curriculum developers, teachers, and students of one another's perceptions as to what is important in and appropriate to teaching and learning in this field of sports medicine. Engagement in the exercise and broader consideration of the outcomes by those who develop the curriculum, teach, and formulate the examination process will facilitate attainment of the ideal of well aligned teaching, learning, and examination in this specific field.

Phosphorylation of a Renatured Protein from Etiolated Wheat Leaf Protoplasts Is Modulated by Blue and Red Light.

Red-light irradiation of etiolated wheat (Triticum aestivum L.) leaf protoplasts rapidly increases calcium-dependent phosphorylation in vivo of 70- and 60-kD peptides, and the phosphorylation is attenuated by simultaneous far-red light (K.M. Fallon, P.S. Shacklock, A.J. Trewavas [1993] Plant Physiology 101:1039-1045). When these protoplasts were solubilized in sodium dodecyl sulfate and protein kinase was renatured in situ after gel electrophoresis, a single 60-kD protein kinase was detected. In situ phosphorylation was inhibited by prior exposure of etiolated protoplasts to 30 to 60 s of white, 1 to 2 min of blue, or 2 to 5 min of red light. The effect of red light was attenuated by concomitant far-red light. The inhibition of in situ phosphorylation by light was lost after a further prolonged incubation of protoplasts in darkness. In situ phosphorylation was calcium dependent, and the electrophoretic mobility of the protein kinase was increased in the presence of calcium ions. Although treatment of protoplasts with ionophores and channel blockers produced data consistent with in vivo regulation of phosphorylation by cytosol calcium, additional light-activated transduction pathways have to be invoked to explain all the observations.

Detection in Vivo of Very Rapid Red Light-Induced Calcium-Sensitive Protein Phosphorylation in Etiolated Wheat (Triticum aestivum) Leaf Protoplasts.

Etiolated wheat (Triticum aestivum cv Mercia) leaf protoplasts respond to brief red-light irradiation by increasing in volume over a 10-min incubation period (M.E. Bossen, H.A. Dassen, R.E. Kendrick, W.J. Vredenberg [1988] Planta 174: 94-100). When the calcium-sensitive dye Fluo-3 was incorporated into these protoplasts, red-light irradiation initiated calcium transients lasting about 2 min (P.S. Shacklock, N.D. Read, A.J. Trewavas [1992] Nature 358: 153-155). Release of calcium in the protoplasts by photolysis of incorporated 1-{2-amino-5-[1-hydroxy-1-(2-nitro-4, 5-methylenedioxyphenyl)-methyl]-phenoxy}-2-(2[prime]-amino-5[prime]-methylp henoxy)-ethane-N,N, N[prime],N[prime] -tetraccetic acid, tetrasodium salt (caged calcium) or caged inositol trisphosphate frequently induced transient increases in intracellular calcium levels, although the kinetics of these changes showed variation between experiments. Upon exposure to red light, a pronounced increase in the phosphorylation of a 70-kD and to a lesser extent a 60-kD peptide was observed, commencing within 15 s and continuing for up to 2 min. Simultaneous far-red and red irradiation attenuated the response. Upon release of incorporated caged calcium by cage photolysis, the labeling of these two peptides was greatly increased. When incorporated caged inositol trisphosphate was photolyzed, only the labeling of the 70-kD peptide was enhanced. Phosphorylation of the 70-kD peptide was also increased when extracellular calcium was elevated, but it decreased with increasing extracellular EGTA. These data thus provide direct evidence for the operation of an in vivo transduction sequence involving red light-dependent, calcium-sensitive protein phosphorylation.

Harlequin syndrome in two athletes.

Two cases are reported of harlequin syndrome, a disorder of the sympathetic nervous system in which sweating and flushing of the skin in response to exercise is diminished. This condition is most likely to be first noticed in sporting situations.