Transplantation of stem cell-derived cardiomyocytes is one of the most promising therapeutic approaches after myocardial infarction, as loss of cardiomyocytes is virtually irreversible by endogenous repair mechanisms. In myocardial scars, transplanted cardiomyocytes will be in immediate contact with cardiac fibroblasts. While it is well documented how the electrophysiology of neonatal cardiomyocytes is modulated by cardiac fibroblasts of the same developmental stage, it is unknown how adult cardiac fibroblasts (aCFs) affect the function of embryonic stem cell-derived cardiomyocytes (ESC-CMs). To investigate the effects of aCFs on ESC-CM electrophysiology, we performed extra- and intracellular recordings of murine aCF-ESC-CM cocultures. We observed that spontaneous beating behaviour was highly irregular in aCF-ESC-CM cocultures compared to cocultures with mesenchymal stem cells (coefficient of variation of the interspike interval: 40.5 ± 15.2% versus 9.3 ± 2.0%, p = 0.008) and that action potential amplitude and maximal upstroke velocity (V max) were reduced (amplitude: 52.3 ± 1.7 mV versus 65.1 ± 1.5 mV, V max: 7.0 ± 1.0 V/s versus 36.5 ± 5.3 V/s), while action potential duration (APD) was prolonged (APD50: 25.6 ± 1.0 ms versus 16.8 ± 1.9 ms, p < 0.001; APD90: 52.2 ± 1.5 ms versus 43.3 ± 3.3 ms, p < 0.01) compared to controls. Similar changes could be induced by aCF-conditioned medium. We conclude that the presence of aCFs changes automaticity and induces potentially proarrhythmic changes of ESC-CM electrophysiology.

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The greater blood loss in SHR than in WKY when bleeding down to a given arterial pressure results from a stronger constriction of venous capacitance vessels. Hyperoxia improves the ability of the cardiorespiratory system to resist the effects of hemorrhage by increasing the overall venous tone, thus supporting cardiac filling, and in some cases also by increasing alveolar ventilation, probably secondary to improved cerebral oxygenation. The beneficial effects of hyperoxia were: (i) not prevented by carotid denervation, and thus were presumably direct tissue effects of oxygen, (ii) strikingly weaker in SHR than in normotensive (WKY) rats.

Increased erythrocyte sodium-lithium countertransport activity has been implicated in the pathogenesis of diabetic nephropathy. However, its relationship to other cation membrane transport systems in incipient nephropathy is not yet clear. The present study was thus performed to: (1) explore associations between sodium-lithium countertransport and changes in the activity of other cation transport pathways and (2) to compare the sodium transport activities with clinical characteristics of insulin-dependent diabetic patients with and without evidence of incipient diabetic nephropathy. We measured erythrocyte sodium-lithium countertransport, passive sodium/potassium flux (at 1 degree C), adenine nucleotide content in intact erythrocytes and sodium/potassium-, magnesium- and calcium-dependent ATPase activity in erythrocyte membrane preparations from 34 insulin-dependent diabetic patients without microalbuminuria, 8 diabetic patients with microalbuminuria, and 8 age-matched healthy control subjects. Sodium-lithium countertransport was elevated in diabetic patients with normo- and microalbuminuria compared with control subjects [268 +/- 99 and 299(277-465), respectively, vs. 166 +/- 65 mumol/(1 cells x h)] and was positively correlated (r = 0.36, P < 0.05) with the albumin excretion rate. However, the activity of erythrocyte membrane ATPases was significantly decreased compared with control subjects. The ATP and ADP content was found to be significantly higher (P < 0.001) in erythrocytes from diabetic patients compared with control subjects (1,196 +/- 276 vs. 833 +/- 253 mumol/l cells and 353 +/- 97 vs. 255 +/- 64 mumol/l cells, respectively). The extent of erythrocyte potassium leakage correlated with hemoglobin A1c (r = 0.39, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The CHIG/Han subline of the Chinese hamster develops noninsulin-dependent diabetes mellitus characterized by hyperinsulinemia and different degrees of glucose intolerance. To study whether these abnormalities could affect transmembrane cation transport activity, we determined membrane ATPase activity and ATP concentrations in red blood cells of diabetes-resistant CHIA and diabetes-susceptible CHIG sublines of the Chinese hamster. Mg(2+)-ATPase activity was increased in red blood cell membranes of diabetic hamsters compared with that of nondiabetic CHIG and the diabetes-resistant CHIA animals and correlated with plasma triglyceride and cholesterol levels. Ca(2+)-ATPase and Na+/K+ATPase activity were not significantly different between diabetic and nondiabetic hamsters, but for the Na+/K(+)-ATPase, Km was decreased and the Vmax value increased in membrane preparations from severely diabetic hamsters. Both ATP and ADP content were lower in erythrocytes from diabetic than nondiabetic hamsters. Independently of the levels of glycemia, AMP concentrations were higher in CHIG than in CHIA hamsters. While ATP/AMP ratios were found to be decreased in erythrocytes from diabetes-susceptible CHIG hamsters compared to the diabetes-resistant CHIA animals, they were significantly correlated with the levels of glycemia. Furthermore, the relationship between blood glucose levels and kidney weight in hamsters of the diabetes-susceptible CHIG subline was such, that severely hyperglycemic animals displayed the greatest increase in kidney wet weight. These results indicate that the progressive metabolic deterioration in the development of noninsulin-dependent diabetes is associated with significant changes in the activity and kinetic parameters of cellular ATPases which could probably indicate early membrane alterations which may eventually result in the late microangiopathic complications of diabetes.

Objectives Our objective was to assess immune responses and their influencing factors in people living with HIV after messenger RNA (mRNA)‐based COVID‐19 booster vaccination (third dose). Methods This was a retrospective cohort study of people living with HIV who received booster vaccination with BNT‐162b2 or mRNA‐1273 between October 2021 and January 2022. We assessed anti‐spike receptor‐binding domain (RBD) immunoglobulin G (IgG), virus neutralizing activity (VNA) titres reported as 100% inhibitory dilution (ID100), and T‐cell response (using interferon‐gamma‐release‐assay [IGRA]) at baseline and quarterly follow‐up visits. Patients with reported COVID‐19 during follow‐up were excluded. Predictors of serological immune response were analyzed using multivariate regression models. Results Of 84 people living with HIV who received an mRNA‐based booster vaccination, 76 were eligible for analysis. Participants were on effective antiretroviral therapy (ART) and had a median of 670 CD4+cells/μL (interquartile range [IQR] 540–850). Following booster vaccination, median anti‐spike RBD IgG increased by 705.2 binding antibody units per millilitre (BAU/mL) and median VNA titres increased by 1000 ID100 at the follow‐up assessment (median 13 weeks later). Multivariate regression revealed that time since second vaccination was a predictor of stronger serological responses (p < 0.0001). No association was found for other factors, including CD4+ status, choice of mRNA vaccine, or concomitant influenza vaccination. In total, 45 patients (59%) had a reactive baseline IGRA, of whom two lost reactivity during follow‐up. Of 31 patients (41%) with non‐reactive baseline IGRA, 17 (55%) converted to reactive and seven (23%) remained unchanged following booster vaccination. Conclusions People living with HIV with ≥500 CD4+cells/μL showed favourable immune responses to mRNA‐based COVID‐19 booster vaccination. A longer time (up to 29 weeks) since second vaccination was associated with higher serological responses, whereas choice of mRNA vaccine or concomitant influenza vaccination had no impact.

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