Retinoic acid accelerates embryonic stem cell-derived cardiac differentiation and enhances development of ventricular cardiomyocytes

Pluripotent embryonic stem (ES) cells spontaneously differentiate via embryo-like aggregates into cardiomyocytes of pacemaker-, atrium- and ventricle-like type, which can be distinguished by their specific patterns of action potentials. It has been shown that retinoic acid (RA) treatment during ES cell differentiation increases the number of cardiomyocytes in a time- and concentration-dependent manner. In order to test the effect of RA on cardiomyocyte differentiation and specialization into ventricle-like cardiomyocytes, we studied gene expression of beta-galactosidase driven by the ventricular myosin light chain-2 (MLC-2v) promoter as an indicator for ventricular differentiation. Clones containing the stably integrated expression vector pGNA/MLC-2.1 were selected, which revealed an increase of beta-galactosidase activity in cardiomyocytes of embryoid bodies at day 7 + 16. RA, both, in the all-trans and in the 9-cis configuration resulted in a significant acceleration of cardiomyocyte differentiation and a transient increase of beta-galactosidase activity. To test whether this acceleration of cardiac differentiation and RA-induced increase of the MLC-2v promotor/beta-galactosidase activity reflects an increase of cardiac- and ventricle-specific gene expression, a semi-quantitative RT-PCR analysis was performed for alpha-cardiac myosin heavy chain (alpha-MHC) and MLC-2v genes. It was shown that both 10(-8) M and 10(-9) M RA resulted in an increased level of alpha-cardiac MHC and MLC-2v mRNA in embryoid bodies in early, but not in terminal developmental stages. This led us to the conclusion that the RA-induced accelerated expression of cardiac-specific genes results in an enhanced development of ventricular cardiomyocytes. An increased number of ventricle-like cells after RA treatment was also found by patch-clamp analysis. The number of cardiomyocytes with Purkinje- and ventricle-like properties was shown to be increased by RA, whereas the number of pacemaker- and atrium-like cells was reduced and early pacemaker cells were not quantitatively affected.

A prognostic score for patients with lower risk myelodysplastic syndrome

Current prognostic models for myelodysplastic syndromes (MDS) do not allow the identification of patients with lower risk disease and poor prognosis that may benefit from early therapeutic intervention. We evaluated the characteristics of 856 patients with low or intermediate-1 disease by the International Prognostic Scoring System. Mean follow-up was 19.6 months (range 1-262). Of these patients, 87 (10%) transformed to acute myelogenous leukemia, and 429 (50%) had died. By multivariate analysis, characteristics associated with worse survival (P<0.01) were low platelets, anemia, older age, higher percent of marrow blasts and poor-risk cytogenetics. Although not included in the model, higher ferritin (P=0.007) and beta2-microglobulin (P<0.001) levels were associated with worse prognosis. This allowed the development of a scoring system in which patients could be grouped in three categories: category 1 (n=182, 21%) with a median survival of 80.3 months (95% CI 68-NA); category 2 (n=408, 48%) with a median survival of 26.6 months (95% CI 22-32) and category 3 (n=265, 31%) with a median survival of 14.2 months (95% CI 13-18). In summary, this analysis indicates that it is possible to identify patients with lower risk MDS and poor prognosis who may benefit from early intervention.

Differentiation of pluripotent embryonic stem cells into the neuronal lineage in vitro gives rise to mature inhibitory and excitatory neurons

Embryonic stem (ES) cells represent a suitable model to analyze cell differentiation processes in vitro. Here, we report that pluripotent ES cells of the line BLC 6 differentiate in vitro into neuronal cells possessing the complex electrophysiological and immunocytochemical properties of postmitotic nerve cells. In the course of differentiation BLC 6-derived neurons differentially express voltage-dependent (K+, Na+, Ca2+) and receptor-operated (GABAA, glycine, AMPA, NMDA receptors) ionic channels. They generate fast Na(+)-driven action potentials and are functionally coupled by inhibitory (GABAergic) and excitatory (glutamatergic) synapses as revealed by measurements of postsynaptic currents. Moreover, BLC 6-derived neurons express neuron-specific cytoskeletal, cell adhesion and synaptic vesicle proteins and exhibit a Ca(2+)-dependent GABA secretion. Thus, the ES cell model enables the investigation of cell lineage determination and signaling mechanisms in the developing nervous system from a pluripotential stem cell to a differentiated postmitotic neuron. The in vitro differentiation of neurons from ES cells may be an excellent approach to study by targeted gene disruption a variety of neuronal functions.

Total, LDL, and HDL cholesterol decrease with age in older men and women. The Rancho Bernardo Study 1984-1994

BACKGROUND

The purpose of the present study was to study the effects of age, weight change, and covariates on lipid and lipoprotein levels cross-sectionally and prospectively in an elderly population.

METHODS AND RESULTS

A community-based sample of 1041 men and 1303 women aged 50 to 93 years was studied cross-sectionally in 1984 to 1987, with follow-up of 372 men and 545 women 8 years later. In the cross-sectional study, levels of total cholesterol (TC) and LDL cholesterol (LDL-C) decreased and levels of HDL cholesterol (HDLC) increased with age in men (all P < .001) but not in women. In the prospective study, TC, LDL-C, and HDL-C levels all decreased in both men and women, in all age groups (50 to 64 years, 65 to 74 years, and > or = 75 years) and in all weight change groups (> 2.5-kg loss, change within 2.5 kg, and > 2.5-kg gain) and in all waist girth change groups, for an overall decrement of approximately 1% per year. In multiple linear regression models, change in weight was the most important independent and consistent predictor of changes in TC, LDL-C, and HDL-C. Similar results were obtained in analyses excluding subjects taking lipid-lowering drugs or estrogen and in analyses adjusted for changes in cigarette smoking, alcohol intake, physical activity, medication use, and incident myocardial infarction, cancer, or diabetes.

CONCLUSIONS

Cross-sectional decrements in TC and LDL-C with age in men are not explained by survivor bias because they are also observed prospectively. Although weight change was the most important explanatory variable, TC, LDL-C, and HDL-C levels also decreased in those who lost or gained weight. Age was not an independent predictor of change. Other prospective studies are recommended to better define the causes and consequences of cholesterol and lipoprotein changes in old age.

Response inhibition and ADHD traits: correlates and heritability in a community sample

Endophenotypes or intermediate phenotypes are of great interest in neuropsychiatric genetics because of their potential for facilitating gene discovery. We evaluated response inhibition, latency and variability measures derived from the stop task as endophenotypes of ADHD by testing whether they were related to ADHD traits in the general population, heritable and shared genetic risk with ADHD traits. Participants were 16,099 children and adolescents, ages 6 to 18 years who visited a local science center. We measured ADHD traits using the Strengths and Weaknesses of ADHD-symptoms and Normal-Behavior (SWAN) rating scale and performance on the stop signal task (SST)-response inhibition (SSRT), response latency (GoRT), and response variability (GoRTSD). Regression analysis was used to assess the relationship of cognitive measures and ADHD traits while controlling for family, age, sex, ethnicity, socioeconomic status and treatment status. Heritability of ADHD and cognitive traits was estimated using SOLAR in 7,483 siblings from 3,507 families that included multiple siblings. Bivariate relationships between pairs of variables were examined. Individuals with greater ADHD trait scores had worse response inhibition, slower response latency, and greater variability. Younger participants and girls had inferior performance although the gender effects were minimal and evident in youngest participants. Inhibition, latency, variability, total ADHD traits, inattention and hyperactivity-impulsivity scores were significantly heritable. ADHD traits and inhibition, but not latency or variability were coheritable. In the largest study in the general population, we found support for the validity of response inhibition as an endophenotype of ADHD.

GHb is a better predictor of cardiovascular disease than fasting or postchallenge plasma glucose in women without diabetes. The Rancho Bernardo Study

OBJECTIVE

To examine the relation between GHb, fasting plasma glucose (FPG), postchallenge plasma glucose (PCPG), and mortality from cardiovascular disease (CVD) and ischemic heart disease (IHD) in older adults.

RESEARCH DESIGN AND METHODS

A community-based study of 1,239 nondiabetic older adults followed for an average of 8 years, from baseline (1984-1987) to 1993.

RESULTS

GHb, but not FPG or PCPG, was significantly related to CVD and IHD mortality in women but not men. The age-adjusted relative hazard for those in the highest quintile of GHb (> or = 6.7%) compared with women with lower levels was 2.37 for fatal CVD (95% CI = 1.30-4.31, P = 0.005) and 2.43 for IHD (95% CI = 1.12-5.25, P = 0.024). This association persisted after adjustment for all covariates (age, systolic blood pressure, BMI, LDL, HDL, triglycerides, cigarette smoking, antihypertensive medication use, and estrogen use). GHb was significantly associated with LDL and HDL levels in women, but the association between GHb and CVD or IHD persisted after adjustment for these lipoproteins.

CONCLUSIONS

We concluded that GHb is a better predictor of CVD and IHD mortality than FPG or PCPG in women without diabetes; no single measure of glycemia was predictive in men. The reason for the sex difference is unexplained.

Primordial germ cell-derived mouse embryonic germ (EG) cells in vitro resemble undifferentiated stem cells with respect to differentiation capacity and cell cycle distribution

Embryonic germ (EG) cells of line EG-1 derived from mouse primordial germ cells were investigated for their in vitro differentiation capacity. By cultivation as embryo-like aggregates EG-1 cells differentiated into cardiac, skeletal muscle and neuronal cells accompanied by the expression of tissue-specific genes and proteins as shown by RT-PCR analysis and indirect immunofluorescence. In comparison to embryonic stem (ES) cells of line D3 the efficiency of differentiation into cardiac and muscle cells was comparatively low, whereas spontaneous neuronal differentiation was more efficient than in D3 cells. Furthermore, the distribution of cell cycle phases as a parameter for the differentiation state was analysed in undifferentiated EG cells and ES cells and compared to data obtained for embryonic carcinoma (EC) cells of line P19 and differentiated, epithelioid EPI-7 cells. Flow cytometric analysis revealed similar cell cycle phase distributions in EG, EC and ES cells. In contrast, the somatic differentiated EPI-7 cells showed a longer G1-phase and shorter S- and G2/M-phases. Together, our results demonstrate that the differentiation state and capacity of EG cells in vitro resemble that of totipotent ES cells.

Opioid receptor agonistic characteristics of mitragynine pseudoindoxyl in comparison with mitragynine derived from Thai medicinal plant Mitragyna speciosa

We have previously elucidated the opiate-like action of mitragynine, an active principle isolated from the Thai medicinal plant Mitragyna speciosa. In the present study, effects of the related compound, mitragynine pseudoindoxyl on electrically stimulated contraction in guinea pig ileum and mouse vas deferens, and on its binding affinity in the guinea pig brain membranes were studied. Mitragynine pseudoindoxyl inhibited the electrically stimulated ileum and mouse vas deferens contractions in a concentration-dependent manner. In the ileum, the effective concentration is in an nM order, being nearly equivalent to reported concentrations of the micro-opioid receptor agonist [D-Ala2, Met-Phe4, Gly-ol5] enkephalin (DAMGO), and is 100- and 20-fold smaller than those of mitragynine and morphine, respectively. In the vas deferens, it is 35-fold smaller than that of morphine. The inhibitory action of mitragynine pseudoindoxyl in the ileum was antagonized by the non-selective opioid receptor antagonist naloxone and the micro-receptor antagonist naloxonazine. It was also antagonized by the delta-receptor antagonist naltrindole in the vas deferens. Mitragynine pseudoindoxyl showed a similar binding affinity to DAMGO and naltrindole at micro- and delta-receptors, respectively. However, the affinity at kappa-receptors was negligible. The present study demonstrates that mitragynine pseudoindoxyl, a novel alkaloid structurally different from other opioid agonists, acts on opioid receptors, leading to a potent inhibition of electrically stimulated contraction in the ileum through the micro-receptors and in mouse vas deferens through delta-receptors.

Phase 1 study of polyethylene glycol formulation of interferon alpha-2B (Schering 54031) in Philadelphia chromosome-positive chronic myelogenous leukemia

Interferon alpha (IFN-alpha) therapy improves prognosis in Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML). Polyethylene glycol (PEG) attached to IFN-alpha prolongs its half-life and may offer better therapy. The aims of this phase 1 study were to define the maximal tolerated dose (MTD), dose-limiting toxicities (DLTs), and response with PEG IFN-alpha-2b. Twenty-seven adults with Ph(+) CML in chronic or accelerated phases, in whom IFN-alpha treatment had failed, were studied. Patients had hematologic (9 patients) or cytogenetic resistance (12 patients) or intolerance to IFN-alpha (6 patients). PEG IFN-alpha-2b was given as a weekly subcutaneous injection starting at 0.75 microg/kg weekly and escalating to 1.5, 3, 4.5, 6, 7.5, and 9.0 microg/kg. The MTD was defined at 7.5 to 9 microg/kg; DLT included severe fatigue, neurotoxicity, liver function abnormalities, and myelosuppression. Longer administration of PEG IFN-alpha-2b resulted in chronic side effects not observed earlier, which defined the MTD and DLT. The proposed phase 2 dose of PEG IFN-alpha-2b was 6 microg/kg weekly. Among 19 patients with active disease, 7 (37%) achieved complete hematologic response (CHR); 2 (11%) had a cytogenetic response (complete). Among 8 patients treated in CHR, 7 (87%) improved cytogenetic response to complete (4 patients) or partial (3 patients). All 6 patients intolerant to IFN-alpha tolerated PEG IFN-alpha-2b; 4 improved their cytogenetic response. The results show that PEG IFN-alpha-2b is easier to deliver (once weekly), better tolerated, and perhaps more effective than IFN-alpha.

Glucose-induced alterations of cytosolic free calcium in cultured rat tail artery vascular smooth muscle cells

We have previously suggested that hyperglycemia per se may contribute to diabetic hypertensive and vascular disease by altering cellular ion content. To more directly investigate the potential role of glucose in this process, we measured cytosolic free calcium in primary cultures of vascular smooth muscle cells isolated from Sprague-Dawley rat tail artery before and after incubation with 5 (basal), 10, 15, and 20 mM glucose. Glucose significantly elevated cytosolic free calcium in a dose- and time-dependent manner, from 110.0 +/- 5.4 to 124.5 +/- 9.0, 192.7 +/- 20.4, and 228.4 +/- 21.9 nM at 5, 10, 15, and 20 mM glucose concentrations, respectively. This glucose-induced cytosolic free calcium elevation was also specific, no change being observed after incubation with equivalent concentrations of L-glucose or mannitol. This glucose effect was also dependent on extracellular calcium and pH, since these calcium changes were inhibited in an acidotic or a calcium-free medium, or by the competitive calcium antagonist lanthanum. We conclude that ambient glucose concentrations within clinically observed limits may alter cellular calcium ion homeostasis in vascular smooth muscle cells. We suggest that these cellular ionic effects of hyperglycemia may underlie the predisposition to hypertension and vascular diseases among diabetic subjects and/or those with impaired glucose tolerance.

Factors associated with bone mineral density in middle-aged men

This cross-sectional population-based study examined the association of anthropometric and lifestyle risk factors with bone mineral density (BMD) in 218 white ambulatory men aged 50-64 from the Rancho Bernardo, California cohort. BMD was measured at the lumbar spine and hip using dual-energy X-ray absorptiometry and at the ultradistal wrist and midshaft radius of the forearm using single-photon absorptiometry. Body mass index (BMI) was significantly correlated with BMD at all four skeletal sites. Overall, 17.0% of men aged 55-64 were osteopenic (BMD > or = 2 SD below the distribution for ages 50-54) at one skeletal site, 16.5% were osteopenic at two sites, and 13.6% were osteopenic at three or more sites. Men who reported regular exercise had significantly higher BMD levels at the spine and hip. Men meeting the recommended daily allowance (RDA) for calcium intake (> or = 800 g/day) had significantly higher BMD levels at the spine and wrist. Alcohol intake and smoking were associated with differences of borderline significance in BMD at the spine. In analyses adjusted for BMI, weight change, exercise, smoking, drinking, and calcium intake, there was a significant independent age-related decline in BMD at the hip (0.008 g/cm2/year; p = 0.001), at the wrist (0.004 g/cm2; p < 0.01), at the forearm (0.006 g/cm2; p < 0.01), but not at the spine (0.005 g/cm2). These data, although cross-sectional, strongly suggest that age-related bone loss occurs in middle-aged men and that both physical activity and an adequate calcium intake are associated with better bone density.

Single-shot measurement of terahertz electromagnetic pulses by use of electro-optic sampling

We demonstrate a simple scheme for capturing the temporal waveforms of a freely propagating terahertz electromagnetic transient in a single shot. The method relies on electro-optic sampling in a noncollinear geometry for the terahertz radiation and the visible probe beam, coupled with multichannel detection. The approach provides time resolution that is comparable to that of conventional electro-optic sampling measurements.

Distribution of preproadrenomedullin mRNA in the rat central nervous system and its modulation by physiological stressors

Adrenomedullin (ADM), encoded by the preproadrenomedullin (ppADM) gene, exerts multiple effects in a wide variety of peripheral and central tissues. Although ADM-like immunoreactivity has been shown to be widely distributed throughout the rat central nervous system (CNS), the detailed distribution of ppADM gene expression in the CNS and its modulation by physiological stimuli remain unknown. In our study, in situ hybridization was used to localize ppADM mRNA in the rat brain and to quantify its levels after exposure to different stressors including lipopolysaccharide (LPS; 100 microg/kg, iv), restraint stress (2 cycles of 1 hour restraint/1 hour rest), and 24 hours of dehydration. In addition, Fos immunoreactivity was used to identify the activation of neurons in response to LPS. Our results show that ppADM mRNA is widely distributed throughout the rat CNS, with especially high levels in autonomic centers including the hypothalamic paraventricular nucleus (PVN), hypothalamic supraoptic nucleus (SON), locus coeruleus, ventrolateral medulla, and intermediolateral cell column of the spinal cord. Furthermore, LPS inhibits ppADM gene expression in the parvocellular PVN (pPVN), magnocellular PVN (mPVN), SON, dorsal motor nucleus of the vagus, and area postrema among examined regions; restraint stress reduces ppADM mRNA levels in the pPVN, mPVN, SON, nucleus of the solitary tract, dorsal motor nucleus of the vagus, area postrema, and subfornical organ; 24 hours of water deprivation decreases ppADM gene expression only in the mPVN and SON. Taken together, our results suggest that ADM is involved in the regulation of the hypothalamo-neurohypophysial system, the hypothalamo-pituitary-adrenal axis, and central autonomic functions.

Binding of an RNA trafficking response element to heterogeneous nuclear ribonucleoproteins A1 and A2

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2 binds a 21-nucleotide myelin basic protein mRNA response element, the A2RE, and A2RE-like sequences in other localized mRNAs, and is a trans-acting factor in oligodendrocyte cytoplasmic RNA trafficking. Recombinant human hnRNPs A1 and A2 were used in a biosensor to explore interactions with A2RE and the cognate oligodeoxyribonucleotide. Both proteins have a single site that bound oligonucleotides with markedly different sequences but did not bind in the presence of heparin. Both also possess a second, specific site that bound only A2RE and was unaffected by heparin. hnRNP A2 bound A2RE in the latter site with a K(d) near 50 nm, whereas the K(d) for hnRNP A1 was above 10 microm. UV cross-linking assays led to a similar conclusion. Mutant A2RE sequences, that in earlier qualitative studies appeared not to bind hnRNP A2 or support RNA trafficking in oligodendrocytes, had dissociation constants above 5 microm for this protein. The two concatenated RNA recognition motifs (RRMs), but not the individual RRMs, mimicked the binding behavior of hnRNP A2. These data highlight the specificity of the interaction of A2RE with these hnRNPs and suggest that the sequence-specific A2RE-binding site on hnRNP A2 is formed by both RRMs acting in cis.

1,25-dihydroxyvitamin D as a cardiovascular hormone. Effects on calcium current and cytosolic free calcium in vascular smooth muscle cells

Clinical and in vitro evidence suggests a role for the calcium regulating hormone, 1,25-dihydroxyvitamin D (1,25D) in human and experimental hypertension. To establish the cellular basis for this association, we utilized the whole-cell version of the patch clamp method and fluorescence spectroscopic techniques to measure voltage-dependent calcium channel activity and cytosolic free calcium concentrations ([Ca2+]i) in rat tail artery-derived smooth muscle cells, before and after the addition of 1,25D. 1,25D significantly increased the calcium channel current over the range of test pulses, from -40 to +60 mV, in a dose- and time-dependent manner, appearing by 5 to 10 min of exposure, with maximum effects by 15 min. At 10 and 30 nmol/L, the current increased to 149 +/- 10% and 221 +/- 13% of basal activity of 37.75 +/- 7.7 pA and 37.7 +/- 4.5 pA, respectively. Similarly, at 10 and 100 nmol/L, 1,25D increased cytosolic free calcium levels 115 +/- 2% and 171 +/- 11%, from basal values of 99 +/- 32 nmol/L and 116 +/- 10 nmol/L, respectively. These effects of [Ca2+]i developed slowly over 3 to 4 min. Peak values were achieved by 30 min of incubation and were reversible with removal of 1,25D from the medium. Altogether, these direct effects of 1,25D on calcium current and [Ca2+]i in vascular smooth muscle cells support a role for 1,25D in vascular physiology, and provide a cellular basis for better understanding the involvement of 1,25D in hypertensive vascular disease.

Specific inhibition of long-lasting, L-type calcium channels by synthetic parathyroid hormone

The effect of an active synthetic N-terminal fragment of bovine parathyroid hormone (bPTH), bPTH-(1-34), on Ca2+ channels was studied in mouse neuroblastoma cells (N1E-115). With the whole-cell variation of the patch-clamp technique, T (transient) and L (long-lasting) types of Ca2+ currents were identified. Pharmacological characterization showed that the L current was amplified by the Ca2+ channel stimulator BAY K-8644, but the T current was unaffected. The administration of bPTH-(1-34) produced dose-related inhibition of the L current, which could be reversed by BAY K-8644. The peptide had no effect on the T current. In addition, use of the fluorescent indicator fura-2 showed that bPTH-(1-34) inhibited the KCl-stimulated increase in intracellular free Ca2+ in neuroblastoma cells with L channels but not in cells with T channels. An inactivated (oxidized) preparation of bPTH-(1-34) failed to affect the L current. High-affinity binding of labeled PTH analog to these neuroblastoma cells was also demonstrated. In addition, bPTH-(1-34) inhibited the L current in cultured vascular smooth muscle cells from rat tail artery. These data indicate that, in some tissues, PTH can act as an endogenous blocker of Ca2+ entry.

Intracerebroventricular adrenomedullin stimulates the hypothalamic-pituitary-adrenal axis, the sympathetic nervous system and production of hypothalamic nitric oxide

We tested the hypothesis that central adrenomedullin stimulates activity of the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic output from the brain, and we assessed the effects of central adrenomedullin on the nitric oxide (NO) system in the brain. In conscious rats, intracerebroventricular (i.c.v.) injections of adrenomedullin (2 nmol/kg) increased arterial pressure and heart rate, with return to baseline values within 20 min and 65 min of injections, respectively. Adrenomedullin injections augmented expression of tyrosine hydroxylase mRNA in the locus coeruleus after 4 h. Plasma concentrations of adrenocorticotropic hormone, measured with radioimmunoassay, were also increased by adrenomedullin. i.c.v. Adrenomedullin stimulated Fos expression in neurones within autonomic centres including the paraventricular nucleus (PVN) of the hypothalamus, arcuate nucleus, locus coeruleus, nucleus of the tractus solitarius and area postrema. In the PVN, large proportions of corticotropin releasing factor- and NO-producing neurones were activated (Fos positive). NO production, measured with nitrate/nitrite assays, was elevated in the hypothalamus, but not brainstem, of adrenomedullin-treated rats compared to controls. We conclude that centrally administered adrenomedullin stimulates activity of the HPA axis, the sympathetic nervous system, and the hypothalamic NO system.

Modulation of sympathetic actions on the heart by opioid receptor stimulation

The sympathetic nervous system, the most important extrinsic regulatory mechanism of the heart, is inhibited postsynaptically and presynaptically by opioid peptides produced in the heart via their respective receptors. The cardiac actions of beta-adrenergic receptor (beta-AR) stimulation are attenuated by activation of the opioid receptor (OR) with OR agonist at ineffective concentrations, implying cross-talk between the OR and beta-AR. This cross-talk results from inhibition of the Gs protein and adenylyl cyclase of the beta-AR pathway by the pertussis toxin-sensitive G protein of the opioid pathway. Alterations in cross-talk between these two receptors occur in pathological situations to meet bodily needs. In myocardial ischemia, when the sympathetic activity is increased, the inhibition of beta-AR stimulation by kappa-opioid stimulation is also enhanced, thus reducing the workload, oxygen consumption and cardiac injury. Whereas cardiac responsiveness to sympathetic discharges is also reduced after chronic hypoxia, the cross-talk between kappa-OR and beta-AR is reduced to prevent undue suppression of the sympathetic influence on the heart. On the other hand, impairment of the cross-talk may result in abnormality. A lack or a significant reduction in the inhibition of beta-AR stimulation by kappa-OR stimulation may lead to an excessive increase in cardiac activities, which contribute to the maintenance of high arterial blood pressure in spontaneously hypertensive rats. Other than opioid peptides, female sex hormone and adenosine also inhibit the sympathetic actions on the heart. In addition, sympathetic action is also inhibited presynaptically by kappa-opioid peptides via their receptor.

Rab6c, a new member of the rab gene family, is involved in drug resistance in MCF7/AdrR cells

A new Rab6 homolog cDNA, Rab6c, was discovered by a hypermethylated DNA fragment probe that was isolated from a human multidrug resistant (MDR) breast cancer cell line, MCF7/AdrR, by the methylation sensitive-representational difference analysis (MS-RDA) technique. Rab6c was found to be under-expressed in MCF7/AdrR and MES-SA/Dx5 (a human MDR uterine sarcoma cell line) compared with their non-MDR parental cell lines. MCF7/AdrR cells expressing the exogenous Rab6c exhibited less resistance to several anti-cancer drugs, such as doxorubicin (DOX), taxol, vinblastine, and vincristine, than the control cells containing the empty vector. Flow cytometry experiments confirmed that the transfectants' diminished resistance to DOX was caused by increased drug accumulation induced by the exogenous Rab6c. These results indicate that Rab6c is involved in drug resistance in MCF7/AdrR cells.

Cardiac effects of the extract and active components of radix stephaniae tetrandrae. II. Myocardial infarct, arrhythmias, coronary arterial flow and heart rate in the isolated perfused rat heart

The primary purpose of the present study was to compare the cardioprotective effects of the extract from radix stephaniae tetrandrae (RST) and its individual compounds, tetrandrine (Tet) and fanchinoline (Fan). Secondly, we also compared the cardiac effects of the individual compounds and the RST extract with those of verapamil, a classical Ca2+ channel blocker. The Langendorff isolated perfused rat heart preparation was used. Regional ischaemia and reperfusion was employed to induce myocardial infarct and arrhythmia. Infarct, arrhythmia, heart rate and coronary artery flow were determined in hearts treated with vehicle, RST extract, Tet, Fan, or verapamil. It was found that RST extract, of which only 9% was Tet, and Tet alone produced equally potent ameliorating effects on arrhythmia and infarct induced by ischaemia and reperfusion without further inhibiting ischaemia-reduced heart rate and coronary artery flow. Fan had no effects on arrhythmia and infarct induced by ischaemia and reperfusion; but it induced S-T segment elevation and further reduced heart rate and coronary artery flow during ischaemia. Verapamil also ameliorated the effects of ischaemia and reperfusion on arrhythmia and infarct. It should be noted that 1 microM verapamil, that produced comparable effects on infarct and arrhythmia to the RST extract and Tet, further inhibited heart rate during ischaemia. The results indicate that the RST extract produces equally potent cardioprotective and anti-arrhythmic effects as Tet alone. Both RST extract and Tet may be better choices for the treatment of arrhythmia and infarct induced by myocardial ischaemia and reperfusion than the classical Ca2+ channel blocker, verapamil as they do not further reduce heart rate during ischaemia.

Optical Coherence in Atomic-Monolayer Transition-Metal Dichalcogenides Limited by Electron-Phonon Interactions

We systematically investigate the excitonic dephasing of three representative transition-metal dichalcogenides, namely, MoS_{2}, MoSe_{2}, and WSe_{2} atomic monolayer thick and bulk crystals, in order to gain a proper understanding of the factors that determine the optical coherence in these materials. Coherent nonlinear optical spectroscopy and temperature dependent absorption, combined with theoretical calculations of the phonon spectra, indicate electron-phonon interactions, to be the limiting factor. Surprisingly, the excitonic dephasing, differs only slightly between atomic monolayers and high quality bulk crystals, which indicates that material imperfections are not the limiting factor in atomically thin monolayer samples. The temperature dependence of the electronic band gap and the excitonic linewidth combined with "ab initio" calculations of the phonon energies and the phonon density of states reveal a strong interaction with the E' and E" phonon modes.

Area postrema ablation attenuates activation of neurones in the paraventricular nucleus in response to systemic adrenomedullin

Adrenomedullin (ADM) is a potent vasodilator in the periphery which also acts centrally to increase blood pressure and inhibit drinking, feeding and salt appetite. This study was designed to study the effects of circulating ADM on neuronal activation in autonomic centres in the rat brain and to examine whether neuronal nitric oxide (NO) may participate in these processes. We identified activated neurones 1 h after intravenous (i.v.) injections of ADM (2 nmol/kg) using immunohistochemistry for Fos. The nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemical reaction was used to localize putative NO-producing neurones and double labelling for Fos and NADPH-d was used to identify activated NO producing neurones. To separate baroreceptor-induced neuronal activation in autonomic centres by ADM from other effects which it may have, i.v. infusions of sodium nitroprusside (NP) were used to mimic the hypotensive effects of ADM in control rats. Significantly greater numbers of activated neurones were found in the paraventricular nucleus of the hypothalamus (PVN) and especially in the dorsolateral medial parvocellular division, the nucleus of the solitary tract, and the area postrema (AP) of ADM-treated rats compared to control rats. In addition, the number of activated NO-producing neurones in the PVN was significantly higher in ADM-treated rats compared to rats treated with NP. To determine whether AP is one of the possible routes through which systemic ADM enters the brain to exert its central effects, the APs of rats were ablated by aspiration. One hour after i.v. injections of ADM, significantly fewer PVN neurones were activated in AP ablation rats compared to AP sham ablation rats. Similarly, the number of activated NO-producing neurones in the PVN was significantly lower in AP ablation rats compared to AP sham ablation rats. In conclusion, our results suggest that systemic ADM gains access to the brain through the AP to regulate neuronal activity in autonomic centres and that neuronal NO might be involved in central autonomic and/or neuroendocrine regulation by ADM.

Mechanism and strategies of immunotherapy resistance in colorectal cancer

Colorectal cancer (CRC) is the third most common cancer in the world. Although there are standard treatment options for CRC, most patients respond poorly to these treatments. Immunotherapies have gradually emerged due to the increasing awareness and understanding of tumor immunity, exhibiting good therapeutic efficacy in various cancers. Immunotherapies include cytokines, immune checkpoint inhibitors (ICIs), and adoptive cell therapies. In particular, ICIs, which are antibodies against cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death 1 (PD-1), or its ligand PD-L1, have been successfully applied clinically for solid tumors, relieving the inhibitory effect of the tumor microenvironment on T cells. However, only a minority of patients with cancer achieve a durable clinical response during immunotherapy. Several factors restrict the efficacy of immunotherapy, leading to the development of drug resistance. In this review, we aimed to discuss the current status of immunotherapy for CRC and elaborate on the mechanisms that mediate resistance to immunotherapy and other potential therapeutic strategies.

Effects of dehydroepiandrosterone sulfate on cellular calcium responsiveness and vascular contractility

Dehydroepiandrosterone sulfate (DHEAS) is an endogenous steroid having a wide variety of biological effects, but its physiological role remains undefined. Since an age-related decline of DHEAS corresponds to the progressive onset of atherosclerosis, cardiovascular diseases, and overall mortality, we investigated a possible protective role of DHEAS in vascular disease by studying the effects of this hormone (10(-7) to 10(-5) mol/L) on cytosolic free calcium and contractility in different in vitro vascular tissue preparations. DHEAS produced a significant, dose-dependent relaxation of isolated helical strips of rat tail artery precontracted with KCl (60 mmol/L) (89.7 +/- 18.7%, P < .01), arginine vasopressin (3 nmol/L) (27.3 +/- 7.1%, P < .01), and norepinephrine (0.1 mumol/L) (49.2 +/- 18.2%, P < .01). In isolated vascular smooth muscle cells DHEAS reversibly inhibited KCl (30 mmol/L)-induced elevations of cytosolic free calcium to 69.8 +/- 8.4% and 43.8 +/- 7.4% of the control response at 5 x 10(-7) and 5 x 10(-6) mol/L, respectively (P < .05 at both doses). These results provide evidence of a direct vascular action of DHEAS, in doses reflecting circulating levels in vivo, and suggest the possibility that these effects are mediated by modulation of intracellular calcium metabolism. We hypothesize that physiologically, DHEAS may serve to buffer vascular responsiveness to a wide variety of depolarizing and constrictor hormonal stimuli.