Association between maternal fasting glucose levels throughout pregnancy and preschoolers' refractive errors.

PURPOSE: We aimed to investigate the association between maternal fasting plasma glucose (FPG) trajectories during pregnancy and children's refractive errors at 6 years old. DESIGN: Based on the Ma'anshan Birth Cohort (MABC) in China, a total of 1987 mother-child pairs were included in this study. METHODS: Using the group-based trajectory model, trajectory fitting was performed on fasting blood glucose levels during the first, second, and third trimesters of pregnancy. Children's vision was measured at 6 years of age using the standard logarithmic visual acuity E-chart and cycloplegic refraction examination. Logistic regression models and multi-informant generalized estimating equations were used to analyze the association between maternal blood glucose level and 6-year-old children's visual acuity. RESULTS: Children born of mothers with high level FPG trajectory had a higher risk of developing refractive error [OR=1.46 (95% CI 1.08 1.97)], hypermetropia [OR=1.64 (95% CI 1.09, 2.46)] and astigmatism [OR=1.60 (95% CI 1.06, 2.41)] at age six compared to those with low level trajectory. Maternal blood glucose level in the first [ß=-0.012 (95% CI -0.024, -0.001)] and the second [ß=-0.016 (95% CI -0.025, -0.006)] trimesters was associated with 6 year children's distance vision value. CONCLUSIONS: High level of fasting plasma glucose trajectories during pregnancy has been observed to be associated with 6-year-old children's refractive error, hypermetropia and astigmatism. The first and the second trimesters may be critical periods for the effects of maternal blood glucose on children's vision. The long-term effect of maternal glucose metabolism on children's visual development deserves further study.

Association between hyperglycemia during pregnancy and offspring's refractive error: A focused review.

This review article explores the relationship between hyperglycemia during pregnancy and the visual development of offspring, specifically focusing on refractive error. The authors conducted a comprehensive search for relevant articles in various databases and assessed the methodological quality of the included studies. The findings consistently indicate that hyperglycemia during pregnancy can have a detrimental impact on the structural and functional aspects of visual development in offspring. The intrauterine hyperglycemic environment appears to negatively affect the retina and lens, leading to refractive errors. In conclusion, there is likely an association between hyperglycemia during pregnancy and the development of refractive errors in offspring.

Sex-specific association between maternal mild anemia and children's behavioral development: a birth cohort study.

There has been limited research on maternal anemia affecting children's behavioral development, with a lack of studies focusing on sex differences in this association. Based on the Ma'anshan Birth Cohort, 2132 mother-child pairs were included. Maternal anemia was evaluated based on the hemoglobin concentration and children's behavioral development was assessed by Achenbach Child Behavior Checklist 1.5-5. Binary logistic regression models indicated that compared with children born of mothers without anemia throughout pregnancy, maternal mild anemia during pregnancy or only anemia in the 3rd trimester was associated with increased risks of aggressive behaviors in boys. Maternal mild anemia only in the 2nd trimester was associated with increased risks of attention problems in boys. In girls, maternal mild anemia during pregnancy was associated with increased risks of withdrawn, internalizing problems and total problems. Girls born of mothers with mild anemia only in the 2nd trimester had higher risks of total problems. Maternal mild anemia in both 2nd and 3rd trimesters was associated with increased risks of internalizing problems in girls. Our study identified sex-specific effects of maternal mild anemia during pregnancy on children's behavioral development problems.

Are there bidirectional associations between maternal thyroid function and glucose metabolism in singleton live births? A birth cohort study.

(1) Aims: To examine the associations between maternal thyroid function and glucose metabolism during pregnancy. (2) Methods: This study was based on Ma' anshan Birth Cohort in China. Totally 2375 pregnant women were included in data analysis. Maternal thyroid-stimulating hormone (TSH), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb) and fasting plasma glucose (FPG) levels during the first, second and third trimesters of pregnancy were measured retrospectively. Mplus 8.0 was used to construct a cross-lagged panel model to examine the potential bidirectional association between thyroid function and FPG levels throughout pregnancy. (3) Results: FT4 levels were positively correlated with FPG levels in the first trimester and negatively correlated with FPG levels in the second trimester. TSH levels were negatively associated with FPG levels in the second trimester, and in the first trimester, it could positively predict FPG levels in the second trimester. No significant association was found between TPOAb levels and FPG levels during pregnancy. (4) Conclusions: There was a non-bidirectional association between maternal thyroid function and glucose metabolism during pregnancy. FT4 and TSH levels influence FPG concentrations in the first and second trimesters of pregnancy.

Association of gestational weight gain rate in pregnant women with children's cognitive and behavioral development: A birth cohort study.

BACKGROUND: The evidences on the relationship between gestational weight gain rate (GWGR) and children's cognitive and behavioral development have been limited. METHODS: A total of 3273 singleton live birth mother-child pairs from the Ma'anshan Birth Cohort in China were included in the study. Maternal GWGR was calculated based on the weights measured at multiple antenatal checkups. Children's cognitive and behavioral development were assessed by Chinese version of Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition and Achenbach Child Behavior Checklist 1.5-5. Then generalized linear models were performed for analyses. RESULTS: In the field of children's cognitive development, excessive GWGR in the second trimester was associated with increased visual space index (VSI), fluid reasoning index (FRI) and full scale intelligence quotient (FSIQ) scores, while excessive GWGR in the third trimester was associated with decreased VSI, working memory index (WMI) and FSIQ scores. In the field of children's behavioral development, excessive GWGR in the second trimester was associated with decreased aggressive behaviors and externalizing problems scores. LIMITATIONS: Children's behavioral development was assessed by main caregivers and might cause a certain degree of bias. There might be other potential confounders that we did not take into account. CONCLUSIONS: A high GWGR in the second trimester might be beneficial for children's cognitive and behavioral development, while a high GWGR in the third trimester might be harmful.

Maternal anxiety during pregnancy and children's asthma in preschool age: The Ma'anshan birth cohort study.

BACKGROUND: The fetal immune system and consequent elevated risk of asthma in childhood may be impacted by maternal anxiety during pregnancy. Limited studies have evaluated whether there was a sensitive period and cumulative effect of the relationship between prenatal anxiety and children's asthma. METHODS: 3131 mother-child pairs made up the study's sample from the Ma'anshan Birth Cohort Study in China. Maternal anxiety status was repeated three times using the pregnancy-related anxiety questionnaire in the 1st, 2nd and 3rd trimesters of pregnancy. Diagnostic information on asthma was collected three times at 24, 36, and 48 months of age. RESULTS: After adjusting for confounders, children born to mothers with anxiety in the 1st, 2nd and 3rd trimesters of pregnancy all had an elevated risk of total asthma from 12 to 48 months of age. After further adjusting prenatal anxiety in the other trimesters, no association was observed between prenatal anxiety in any trimester and preschoolers' asthma. Children of mothers with persistently high anxiety score trajectory during pregnancy had an elevated risk of total asthma and high prevalence trajectory of asthma. Cumulative effects analysis showed that the more frequent the mother's anxiety, the higher the risk of her offspring developing a high prevalence trajectory of asthma from 12 to 48 months of age. The results of the subgroup analysis by age showed similar associations overall. CONCLUSIONS: Maternal antenatal anxiety was associated with an elevated risk of preschool children's asthma, and a possible cumulative effect was observed. Maternal mental health conditions during pregnancy should receive constant attention throughout pregnancy, not just during one period.

Peri-Conceptional Folic Acid Supplementation and Children's Physical Development: A Birth Cohort Study.

BACKGROUND: Maternal lack of folic acid supplementation during pregnancy may increase the risk of low birth weight and preterm delivery. However, little is known about the relationship between folic acid supplementation during pregnancy and the physical development of offspring in the later stage. OBJECTIVE: This study aimed to explore the association between maternal folic acid supplementation status during pregnancy and the physical development of preschool children. METHODS: A total of 3064 mother-child pairs with data on maternal folic acid supplementation status during pregnancy and children's anthropometric measurements were recruited from the Ma'anshan-Anhui Birth Cohort (MABC) in China. Maternal folic acid supplementation status during pregnancy was the main exposure, and the primary outcomes were children's growth development trajectories. Children's growth development trajectories were fitted using group-based trajectory models. The association between maternal folic acid supplementation status during pregnancy and children's growth trajectories was performed using multiple logistic regression models. RESULTS: After adjusting for potential confounders, we found that the absence of maternal folic acid supplementation before pregnancy and in the first trimester was significantly associated with a "high level" trajectory (trajectory 3) and a "high rising level" trajectory (trajectory 4) of BMI-Z scores in children 0 to 6 years of age (OR = 1.423, 95%CI:1.022-1.982; OR = 1.654, 95%CI: 1.024-2.671). In children aged 4 to 6 years old, a "high level" trajectory (trajectory 3) of body fat ratio was substantially related to maternal no folic acid supplementation before pregnancy and in the first trimester (OR = 1.833, 95%CI:1.037-3.240). No significant additional benefits associated with physical developmental indicators in preschool children have been observed with continued folic acid supplementation after the first trimester of gestation. CONCLUSIONS: Maternal non-supplementation with folic acid during pregnancy is associated with a "high level" BMI trajectory and a "high level" body fat ratio trajectory in preschool-aged children.

Maternal Pre-Pregnancy Body Mass Index, Gestational Weight Gain and Children's Cognitive Development: A Birth Cohort Study.

To investigate the joint effect of maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) on children's cognitive development. We recruited 1685 mother-child pairs from the Ma'anshan Birth Cohort in China. Pre-pregnancy BMI and GWG were calculated based on the height and weights measured at multiple antenatal checkups. Children's cognition was assessed by Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition. Poisson regression model was used to analyze the association between maternal pre-pregnancy BMI and children's cognitive dimensions under different GWG categories. Women with overweight or obese before pregnancy were more likely to obtain excessive GWG. When women had excessive GWG, pre-pregnancy overweight was associated with low children's PSI (OR = 1.69, 95%CI: 1.02-2.81) and pre-pregnancy obesity was related to poor VCI in children (OR = 3.71, 95%CI: 1.49-9.22), after adjusting for potential confounders. In pre-pregnancy underweight mothers, adequate GWG reduced the risk of below-average VSI in children (OR = 0.22, 95%CI: 0.05-0.92), but excessive GWG was related to low FSIQ in children (OR = 2.53, 95%CI: 1.34-4.76). In women with excessive GWG, maternal pre-pregnancy BMI displays an inverted U-shape association with children's cognition. Moreover, adequate GWG in women with pre-pregnancy underweight was beneficial for children's cognition.

Non-Linear and Sex-Specific Effect of Maternal Pre-Pregnancy BMI on Emotional and Behavioral Development of Preschool Children: A Population-Based Cohort Study.

(1) Background: The aim was to examine the non-linear and sex-specific outcomes of maternal pre-pregnancy BMI on emotional and behavioral development of preschool children; (2) Methods: This study was based on the China-Anhui Birth Cohort (C-ABCS), including 3648 mother-child pairs. Maternal pre-pregnancy BMI was calculated from the maternal pre-pregnancy height and weight measured at the first antenatal checkup. Main caregivers completed the Strengths and Difficulties Questionnaire (SDQ) to assess children's preschool emotional and behavioral development. A restricted cubic spline model was drawn using Stata version 15.1 to analyze the association between maternal pre-pregnancy BMI and preschoolers' SDQ scores by sex; (3) Results: Among boys, maternal pre-pregnancy underweight was associated with the increased risk of conduct problems and pro-social behaviors, and pre-pregnancy overweight/obesity related with the increased risk of peer problems. Interestingly, when maternal pre-pregnancy BMI was between 18.50 kg/m2 and 18.67 kg/m2, boys had the increased risk of conduct problems. When pre-pregnancy BMI was between 18.50 kg/m2 and 19.57 kg/m2, boys had the increased risk of pro-social problems. No significant associations were observed; (4) Conclusions: A non-linear effect of maternal pre-pregnancy BMI on emotional and behavioral development has been found in preschool boys. In particular, pre-pregnancy normal weight may still affect boys' emotional and behavioral development.

TSPO ligand etifoxine attenuates LPS-induced cognitive dysfunction in mice.

The translocator protein (TSPO), once known as peripheral-type benzodiazepine receptor, was reported to be related with several physiological functions. Etifoxine is a clinically available anxiolytic drug, and has recently shown neuroprotective effects as a TSPO ligand. The aim of the present study was to investigate the influence of etifoxine on LPS-induced neuroinflammation and cognitive dysfunction. C57/BL6 male mice were injected with etifoxine (50 mg/kg, i.p.) three days before lipopolysaccharide (LPS, 500 µg/kg, i.p.) administration. Etifoxine pretreatment alleviated hippocampal inflammation, increased brain levels of progesterone, allopregnanolone and attenuated cognitive dysfunction in LPS-injected mice. While LPS increased expression of caspase-3 and decreased p-Akt/Akt, etifoxine returned caspase-3 and p-Akt/Akt to control levels. Finasteride, a 5α-reductase inhibitor that blocked allopregnanolone production, partially reversed the effects of etifoxine. We concluded that etifoxine exerted neuroprotective effects in LPS-induced neuroinflammation and the neuroprotection may be related with increase of neurosteroids synthesis and decrease of apoptosis.

Robotic-assisted laparoscopic artery-sparing varicocelectomy using indocyanine green fluorescence angiography: Initial experience.

We reported our initial experience of robotic-assisted laparoscopic artery-sparing varicocelectomy using indocyanine green (ICG) fluorescence angiography in treatment of varicocele. A total of 45 varicocelectomies in 27 patients were performed. The mean operation time was 49.1 ± 8.5 min for unilateral and 65.6 ± 8.3 min for bilateral repair. 47.2 s after ICG injection, testicular artery (TA) was visualised. After an interval of 31.3 s, fluorescent veins were identified. Of all the 45 spermatic cords, 68.9% had a solitary artery, while 31.1% had 2 arteries. The mean hospital stay was 1.6 ± 0.9 days. Semen concentration and motility were significantly improved 6 months after surgery, no recurrence, hydrocele or testicular atrophy was observed. Our study demonstrated that robotic-assisted laparoscopic artery-sparing varicocelectomy using ICG fluorescence angiography is a safe, effective and promising technique in treatment of varicocele.

Laparoscopic Yang-Monti Ureteral Reconstruction in Children.

OBJECTIVE: To investigate the clinical outcome of surgical treatment for long ureteral defect in children, we evaluated our experience of managing 6 children with the long defect utilizing laparoscopic ureteral reconstruction technique using Yang-Monti technique. MATERIALS AND METHODS: Six children with long ureteral defect who underwent laparoscopic Yang-Monti ureteral reconstruction between January 2013 and March 2016 were reviewed. The diagnosis and outcomes of long ureteral defects were reviewed based on clinical and imaging data. We assessed preoperative clinical data and outcomes, and analyzed the experience of laparoscopic Yang-Monti ureteral reconstruction. RESULTS: The mean age of the patients was 8.5 years. The etiology of the ureteral defect was failed pyeloplasty in 4 patients, failed pyeloplasty and ureteral reimplantation in 1, and trauma in 1. The mean defect length was 5.83 cm. All operations were performed successfully with no serious intraoperative complications and no conversion. The average operative time was 314 minutes, the average intraoperative blood loss was 25 mL, the average drain removal was 3.83 days, the average start of oral feeding was 5.17 days, and the average postoperative hospital stay was 7.17 days. Six patients suffered Clavien I and II complications postoperatively and were managed conservatively. Two patients suffered Clavien III complications postoperatively and were managed by replacing stent. A diuretic T1/2 showed the improvement of differential renal function without urinary obstruction in all patients. CONCLUSION: Laparoscopic Yang-Monti ureteral reconstruction is safe and feasible in children with an excellent outcome.

Ca2+ cycling in heart cells from ground squirrels: adaptive strategies for intracellular Ca2+ homeostasis.

Heart tissues from hibernating mammals, such as ground squirrels, are able to endure hypothermia, hypoxia and other extreme insulting factors that are fatal for human and nonhibernating mammals. This study was designed to understand adaptive mechanisms involved in intracellular Ca(2+) homeostasis in cardiomyocytes from the mammalian hibernator, ground squirrel, compared to rat. Electrophysiological and confocal imaging experiments showed that the voltage-dependence of L-type Ca(2+) current (I(Ca)) was shifted to higher potentials in ventricular myocytes from ground squirrels vs. rats. The elevated threshold of I(Ca) did not compromise the Ca(2+)-induced Ca(2+) release, because a higher depolarization rate and a longer duration of action potential compensated the voltage shift of I(Ca). Both the caffeine-sensitive and caffeine-resistant components of cytosolic Ca(2+) removal were more rapid in ground squirrels. Ca(2+) sparks in ground squirrels exhibited larger amplitude/size and much lower frequency than in rats. Due to the high I(Ca) threshold, low SR Ca(2+) leak and rapid cytosolic Ca(2+) clearance, heart cells from ground squirrels exhibited better capability in maintaining intracellular Ca(2+) homeostasis than those from rats and other nonhibernating mammals. These findings not only reveal adaptive mechanisms of hibernation, but also provide novel strategies against Ca(2+) overload-related heart diseases.

Beta-adrenergic signaling accelerates and synchronizes cardiac ryanodine receptor response to a single L-type Ca2+ channel.

As the most prototypical G protein-coupled receptor, beta-adrenergic receptor (betaAR) regulates the pace and strength of heart beating by enhancing and synchronizing L-type channel (LCC) Ca(2+) influx, which in turn elicits greater sarcoplasmic reticulum (SR) Ca(2+) release flux via ryanodine receptors (RyRs). However, whether and how betaAR-protein kinase A (PKA) signaling directly modulates RyR function remains elusive and highly controversial. By using unique single-channel Ca(2+) imaging technology, we measured the response of a single RyR Ca(2+) release unit, in the form of a Ca(2+) spark, to its native trigger, the Ca(2+) sparklet from a single LCC. We found that acute application of the selective betaAR agonist isoproterenol (1 microM, < or = 20 min) increased triggered spark amplitude in an LCC unitary current-independent manner. The increased ratio of Ca(2+) release flux underlying a Ca(2+) spark to SR Ca(2+) content indicated that betaAR stimulation helps to recruit additional RyRs in synchrony. Quantification of sparklet-spark kinetics showed that betaAR stimulation synchronized the stochastic latency and increased the fidelity (i.e., chance of hit) of LCC-RyR intermolecular signaling. The RyR modulation was independent of the increased SR Ca(2+) content. The PKA antagonists Rp-8-CPT-cAMP (100 microM) and H89 (10 microM) both eliminated these effects, indicating that betaAR acutely modulates RyR activation via the PKA pathway. These results demonstrate unequivocally that RyR activation by a single LCC is accelerated and synchronized during betaAR stimulation. This molecular mechanism of sympathetic regulation will permit more fundamental studies of altered betaAR effects in cardiovascular diseases.

NAADP mobilizes calcium from acidic organelles through two-pore channels.

Ca(2+) mobilization from intracellular stores represents an important cell signalling process that is regulated, in mammalian cells, by inositol-1,4,5-trisphosphate (InsP(3)), cyclic ADP ribose and nicotinic acid adenine dinucleotide phosphate (NAADP). InsP(3) and cyclic ADP ribose cause the release of Ca(2+) from sarcoplasmic/endoplasmic reticulum stores by the activation of InsP(3) and ryanodine receptors (InsP(3)Rs and RyRs). In contrast, the nature of the intracellular stores targeted by NAADP and the molecular identity of the NAADP receptors remain controversial, although evidence indicates that NAADP mobilizes Ca(2+) from lysosome-related acidic compartments. Here we show that two-pore channels (TPCs) comprise a family of NAADP receptors, with human TPC1 (also known as TPCN1) and chicken TPC3 (TPCN3) being expressed on endosomal membranes, and human TPC2 (TPCN2) on lysosomal membranes when expressed in HEK293 cells. Membranes enriched with TPC2 show high affinity NAADP binding, and TPC2 underpins NAADP-induced Ca(2+) release from lysosome-related stores that is subsequently amplified by Ca(2+)-induced Ca(2+) release by InsP(3)Rs. Responses to NAADP were abolished by disrupting the lysosomal proton gradient and by ablating TPC2 expression, but were only attenuated by depleting endoplasmic reticulum Ca(2+) stores or by blocking InsP(3)Rs. Thus, TPCs form NAADP receptors that release Ca(2+) from acidic organelles, which can trigger further Ca(2+) signals via sarcoplasmic/endoplasmic reticulum. TPCs therefore provide new insights into the regulation and organization of Ca(2+) signals in animal cells, and will advance our understanding of the physiological role of NAADP.

Beta-nicotinamide adenine dinucleotide is an inhibitory neurotransmitter in visceral smooth muscle.

Peripheral inhibitory nerves are physiological regulators of the contractile behavior of visceral smooth muscles. One of the transmitters responsible for inhibitory neurotransmission has been reputed to be a purine, possibly ATP. However, the exact identity of this substance has never been verified. Here we show that beta-nicotinamide adenine dinucleotide (beta-NAD), an inhibitory neurotransmitter candidate, is released by stimulation of enteric nerves in gastrointestinal muscles, and the pharmacological profile of beta-NAD mimics the endogenous neurotransmitter better than ATP. Levels of beta-NAD in superfusates of muscles after nerve stimulation exceed ATP by at least 30-fold; unlike ATP, the release of beta-NAD depends on the frequency of nerve stimulation. beta-NAD is released from enteric neurons, and release was blocked by tetrodotoxin or omega-conotoxin GVIA. beta-NAD is an agonist for P2Y1 receptors, as demonstrated by receptor-mediated responses in HEK293 cells expressing P2Y1 receptors. Exogenous beta-NAD mimics the effects of the enteric inhibitory neurotransmitter. Responses to beta-NAD and inhibitory junction potentials are blocked by the P2Y1-selective antagonist, MRS2179, and the nonselective P2 receptor antagonists, pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid and suramin. Responses to ATP are not blocked by these P2Y receptor inhibitors. The expression of CD38 in gastrointestinal muscles, and specifically in interstitial cells of Cajal, provides a means of transmitter disposal after stimulation. beta-NAD meets the traditional criteria for a neurotransmitter that contributes to enteric inhibitory regulation of visceral smooth muscles.

[Electrophysiology of two human hyperpolarization activated cyclic nucleotide-gated potassium channels expressed in HEK293 cells].

OBJECTIVE: To express the human HCN2 and HCN4 genes in HEK293 cells and investigate the electrophysiology of the expressed channel protein. METHODS: cDNA encoding human HCN2 or HCN4 gene was ligated into a shuttle vector pAdTrack-CMV. Homologous recombination was performed in Escherichia coli of the line BJ5183. Human embryonic kidney cells of the line 293 (HEK293 cells) were cultured and transfected with the positive recombinant adenovirus plasmid. Then the HEK293 cells were infected by AdhHCN2 or AdhHCN4 and the whole cell hyperpolarization-activated currents were recorded in HEK293 cells transfected with hHCN2 and hHCN4. RESULTS: If-like currents could be found in the HEK293 cells transfected with hHCN2 and hHCN4. The channels were activated by hyperpolarized potentials. Boltzmann equation showed that the half-activation voltage of the hHCN2 and hHCN4 channels were -114.8 mV +/- 3.3 mV and -125.9 mV +/- 2.9 mV respectively (P = 0.024). The reversal slope factors of the hHCN2 and hHCN4 channels were 11.1 mV +/- 1.2 mV and 13.7 mV +/- 1.3 mV respectively (P = 0.22). The activation kinetics was faster in hHCN2 than in hHCN4, with the activation constants at -110 mV being 0.99 s +/- 0.21 s and 8.47 s +/- 2.85 s respectively. The relative permeation ratio for sodium and potassium were 0.40 and 0.34 respectively in these two channels. Caesium chloride of the concentration of 2 mmol/L prominently inhibited both currents. CONCLUSION: The target genes hHCN2 and hHCN4 are successfully expressed in HEK293 cells, and the expressed functional channels have profoundly different activation kinetics.

Intermolecular failure of L-type Ca2+ channel and ryanodine receptor signaling in hypertrophy.

Pressure overload-induced hypertrophy is a key step leading to heart failure. The Ca(2+)-induced Ca(2+) release (CICR) process that governs cardiac contractility is defective in hypertrophy/heart failure, but the molecular mechanisms remain elusive. To examine the intermolecular aspects of CICR during hypertrophy, we utilized loose-patch confocal imaging to visualize the signaling between a single L-type Ca(2+) channel (LCC) and ryanodine receptors (RyRs) in aortic stenosis rat models of compensated (CHT) and decompensated (DHT) hypertrophy. We found that the LCC-RyR intermolecular coupling showed a 49% prolongation in coupling latency, a 47% decrease in chance of hit, and a 72% increase in chance of miss in DHT, demonstrating a state of "intermolecular failure." Unexpectedly, these modifications also occurred robustly in CHT due at least partially to decreased expression of junctophilin, indicating that intermolecular failure occurs prior to cellular manifestations. As a result, cell-wide Ca(2+) release, visualized as "Ca(2+) spikes," became desynchronized, which contrasted sharply with unaltered spike integrals and whole-cell Ca(2+) transients in CHT. These data suggested that, within a certain limit, termed the "stability margin," mild intermolecular failure does not damage the cellular integrity of excitation-contraction coupling. Only when the modification steps beyond the stability margin does global failure occur. The discovery of "hidden" intermolecular failure in CHT has important clinical implications.

Temperature dependence and thermodynamic properties of Ca2+ sparks in rat cardiomyocytes.

To elucidate the temperature dependence and underlying thermodynamic determinants of the elementary Ca2+ release from the sarcoplasmic reticulum, we characterized Ca2+ sparks originating from ryanodine receptors (RyRs) in rat cardiomyocytes over a wide range of temperature. From 35 degrees C to 10 degrees C, the normalized fluo-3 fluorescence of Ca2+ sparks decreased monotonically, but the Delta[Ca2+]i were relatively unchanged due to increased resting [Ca2+]i. The time-to-peak of Ca2+ sparks, which represents the RyR Ca2+ release duration, was prolonged by 37% from 35 degrees C to 10 degrees C. An Arrhenius plot of the data identified a jump of apparent activation energy from 5.2 to 14.6 kJ/mol at 24.8 degrees C, which presumably reflects a transition of sarcoplasmic reticulum lipids. Thermodynamic analysis of the decay kinetics showed that active transport plays little role in early recovery but a significant role in late recovery of local Ca2+ concentration. These results provided a basis for quantitative interpretation of intracellular Ca2+ signaling under various thermal conditions. The relative temperature insensitivity above the transitional 25 degrees C led to the notion that Ca2+ sparks measured at a "warm room" temperature are basically acceptable in elucidating mammalian heart function.