Effects of thyroxine and 1-methyl, 2-mercaptoimidazol on phosphoinositides synthesis in rat liver

Background  

Phosphoinositides mediate one of the intracellular signal transduction pathways and produce a class of second messengers that are involved in the action of hormones and neurotransmitters on target cells. Thyroid hormones are well known regulators of lipid metabolism and modulators of signal transduction in cells. However, little is known about phosphoinositides cycle regulation by thyroid hormones. The present paper deals with phosphoinositides synthesis de novo and acylation in liver at different thyroid status of rats.     

Acquired thrombotic thrombocytopenic purpura: puzzles,curiosities and conundrums

We report a case of acquired thrombotic thrombocytopenic purpura (TTP) in a 34-year old patient with a prior diagnosis of systemic lupus erythematosis (SLE) who was recently started on hydroxychloroquine. Presenting symptoms included fevers, sore throat and productive cough with progressive weakness, dyspnea on exertion, hemoptysis and dark urine. Initial laboratory abnormalities were consistent with an acute microangiopathic hemolytic anemia and severe thrombocytopenia. At the time of admission, the patient’s lupus was highly active as evident by his high SLE Disease Activity Index (SLEDAI) score. He was later also found to have severely reduced ADAMTS-13 levels and a positive antibody assay. This case highlights the occasional difficulty in pinpointing the exact etiology of TTP as well as establishes a possible novel drug association between hydroxychloroquine and TTP development.     

Dissemination of Misinformative and Biased Information about Prostate Cancer on YouTube

YouTube is a social media platform with more than 1 billion users and >600 000 videos about prostate cancer. Two small studies examined the quality of prostate cancer videos on YouTube, but did not use validated instruments, examine user interactions, or characterize the spread of misinformation. We performed the largest, most comprehensive examination of prostate cancer information on YouTube to date, including the first 150 videos on screening and treatment. We used the validated DISCERN quality criteria for consumer health information and the Patient Education Materials Assessment Tool, and compared results for user engagement. The videos in our sample had up to 1.3 million views (average 45 223) and the overall quality of information was moderate. More videos described benefits (75%) than harms (53%), and only 50% promoted shared decision-making as recommended in current guidelines. Only 54% of the videos defined medical terms and few provided summaries or references. There was a significant negative correlation between scientific quality and viewer engagement (views/month p = 0.004; thumbs up/views p = 0.015). The comments section underneath some videos contained advertising and peer-to-peer medical advice. A total of 115 videos (77%) contained potentially misinformative and/or biased content within the video or comments section, with a total reach of >6 million viewers.

Increased SR Ca2+ cycling contributes to improved contractile performance in SERCA2a-overexpressing transgenic rats

OBJECTIVE: Heart failure is associated with reduced function of sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a) but increased function of sarcolemmal Na+/Ca2+ exchanger (NCX), leading to decreased SR Ca2+ content and loss of frequency-potentiation of contractile force. We reported that SERCA2a-overexpression in transgenic rat hearts (TG) results in improved contractility. However, it was not clear whether TG have improved contractility due to frequency-dependent improved SR Ca2+ handling. METHODS: Therefore, we characterized TG (n=35) vs. wild-type (WT) control rats (n=39) under physiological conditions (37 degrees C, stimulation rate <8 Hz). Twitch force, intracellular Ca2+ transients ([Ca2+]i), and SR Ca2+ content were measured in isolated muscles. The contribution of transsarcolemmal Ca2+ influx (I(Ca)) through L-type Ca2+ channels (LTCC) and reverse mode NCX (I(Na/Ca)) to Ca2+ cycling were studied in isolated myocytes. RESULTS: With increasing frequency, force increased in TG muscles by 168+/-35% (8 Hz; P<0.05) and SR Ca2+ content increased by maximally 118+/-31% (4 Hz; P<0.05). In WT, there was a flat force-frequency response without changes in SR Ca2+ content. Relaxation parameters of force and [Ca2+]i decay were accelerated at each frequency in TG vs. WT by approximately 10%. At prolonged rest intervals (<240 s), force and SR Ca2+ content increased significantly more in TG. Consequently, absolute SR Ca2+ content measured in myocytes was increased approximately 2-fold in TG. Transsarcolemmal Ca2+ fluxes estimated by I(Ca) (at 0 mV -10.2+/-1.1 vs. -16.9+/-1.3 pA/pF) and I(Na/Ca) (0.17+/-0.02 vs. 0.46+/-0.05 pA/pF) were decreased in TG vs. WT (P<0.05), whereas NCX and LTCC protein expression was only slightly reduced (P=n.s.). CONCLUSION: In summary, SERCA2a-overexpression improved contractility in a frequency-dependent way due to increased SR Ca2+ loading whereas transsarcolemmal Ca2+ fluxes were decreased.     

N-cadherin haploinsufficiency affects cardiac gap junctions and arrhythmic susceptibility

Cardiac-specific deletion of the murine gene (Cdh2) encoding the cell adhesion molecule, N-cadherin, results in disassembly of the intercalated disc (ICD) structure and sudden arrhythmic death. Connexin 43 (Cx43)-containing gap junctions are significantly reduced in the heart after depleting N-cadherin, therefore we hypothesized that animals expressing half the normal levels of N-cadherin would exhibit an intermediate phenotype. We examined the effect of N-cadherin haploinsufficiency on Cx43 expression and susceptibility to induced arrhythmias in mice either wild-type or heterozygous for the Cx43 (Gja1)-null allele. An increase in hypophosphorylated Cx43 accompanied by a modest decrease in total Cx43 protein levels was observed in the N-cadherin heterozygous mice. Consistent with these findings N-cadherin heterozygotes exhibited increased susceptibility to ventricular arrhythmias compared to wild-type mice. Quantitative immunofluorescence microscopy revealed a reduction in size of large Cx43-containing plaques in the N-cadherin heterozygous animals compared to wild-type. Gap junctions were further decreased in number and size in the N-cad/Cx43 compound heterozygous mice with increased arrhythmic susceptibility compared to the single mutants. The scaffold protein, ZO-1, was reduced at the ICD in N-cadherin heterozygous cardiomyocytes providing a possible explanation for the reduction in Cx43 plaque size. These data provide further support for the intimate relationship between N-cadherin and Cx43 in the heart, and suggest that germline mutations in the human N-cadherin (Cdh2) gene may predispose patients to increased risk of cardiac arrhythmias.