Preservation of left ventricle peak and mean pulse flow blood velocity despite progressive deterioration of cardiac function in a chronic heart failure murine model

The goal of this study was to assess the alterations in left ventricle (LV) blood flow velocity patterns in relation to progressive impairment of cardiac function in the course of heart failure (HF) in a unique murine model of chronic HF in Tgαq*44 mice. Doppler- and MRI-based assessments of blood velocity and cardiac performance, respectively, were performed in Tgαq*44 mice at the age of 1, 2, 4, 6, 8 and 12 months as compared with age-matched FVB control mice. One-month-old Tgαq*44 mice displayed elongated early diastolic phase with fully preserved cardiac function that, however, progressively deteriorated in older Tgαq*44 mice. As early as in 2-month-old Tgαq*44 mice, the filling rate (FR), max. radial strain and end-systolic volume increased; in 4-month-old Tgαq*44 mice, the ejection fraction, max. circ. strain and ventriculo-arterial coupling decreased, and the ejection time was prolonged; in 6 - 8-month-old Tgαq*44 mice, the stroke volume, max. (both) strains decreased, end-systolic volume, FR and end-diastolic volume increased, and finally, in 12-month-old Tgαq*44 mice, the ejection fraction, cardiac output and stroke volume were all severely impaired. In the early phase of HF development, no differences were observed in Tgαq*44 mice versus FVB mice regarding systolic LV flow pattern, but indices of mitral diastolic flow were considerably increased in 1-month-old Tgαq*44 mice versus FVB mice. In the late phase of HF, despite progressive deterioration of cardiac function, LV pulse flow blood velocity was not altered in Tgαq*44 mice up to the age of 8 months. Systolic peak velocity and mean acceleration time deteriorated only in 12-month-old Tgαq*44 mice, with peak acceleration and mean velocity values still preserved. We demonstrated that the cardiac mitral diastolic flow pattern displayed adaptive changes in the very early phase of HF development in Tgαq*44 mice and that these changes preceded early alterations in LV haemodynamics. Then, despite the progressive deterioration of cardiac haemodynamics, peak and mean in- and out-flow velocities remained unchanged for a relatively long time and deteriorated only at the end-stage HF. Altogether, we revealed that in addition to cardiac performance, adaptive vascular performance represents an important factor determining LV mitral inflow and ejection flow phenotype during the progression of chronic HF in Tgαq*44 mice.

Age-dependent cardiac remodelling – role of sex hormones

Background

While cardiovascular mortality in women has exceeded those in men, women continue to be underrepresented in cardiovascular clinical trials. Further, preclinical experiments are predominantly conducted in male animals, rendering sex-specific variables contributing to cardiovascular disease largely unknown. As age and menopause remain to be key risk factors for cardiovascular disease in women, the aim of this study was to identify key variables of cardiac remodelling in the aging female and male heart, as well as to assess effects of sex hormone deprivation on left ventricular (LV) morphology, LV function and cardiac sympathetic activity.

Materials and methods

Gonadectomized and sham-operated FVB/N mice of both sexes were subjected to positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging at the age of 4 (young cohort) and 20 (aged cohort) months (total n=123, 55% females). Following tail-vein injection of [11C]meta-hydroxynorephedrine ([11C]mHED), a widely used PET probe in preclinical and clinical assessment of cardiac sympathetic integrity, animals were scanned and cardiac sympathetic outflow was derived from myocardial [11C]mHED uptake. Cardiac parameters including LV volumes and left ventricular ejection fraction (LVEF) were obtained from electrocardiogram (ECG)-gated CMR imaging.

Results and discussion

A significant increase of LVEF was observed in aging females (p=0.012, Figure 1), but not in males. The latter was not associated with a higher cardiac output, and was a consequence of reduced LV end-systolic volumes (p=0.008), unveiling a substantial reduction of size in the aging female heart. As this age-dependent observation was not present in gonadectomized animals (p=0.414), the lack of growth-stimulating estrogen might account for reduction of cardiac size in aging females. Thus, despite a significantly heightened body weight, female heart size is reduced with age. Accordingly, sufficient cardiac output was maintained via increased heart rate (p=0.005) and cardiac sympathetic activity (p=0.040, Figure 1). Gonadectomy accelerated age-dependent changes in LV morphology and function in female mice. While sex hormone deprivation blunted cardiac sympathetic activity and norepinephrine levels in male mice, an opposite trend was observed in females.

Conclusion

Despite increasing body weight with age, aged female and male hearts maintain a stable circulatory blood supply, however, by distinct mechanisms. While the “shrinking” female heart requires an increased heart rate and cardiac sympathetic activity to compensate for smaller ventricular volumes, aging males maintain cardiac size. Importantly, sex hormone deprivation at a young age accelerates age-dependent changes in LV morphology and function in female mice, but not in male mice. The increased sympathetic activity reflects a higher stress level in aged females that might expose them to a higher cardiac vulnerability at postmenopausal age.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation; Swissheart Foundation

Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives

Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E′0 values between -0 .3 8 V and -0 .6 V. Compounds of E′0 values of -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities of these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4′-bipyridini urn bromide with an E′0 value of lower -1 V (and thus no electron acceptor of photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub­ chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position of the pyridinium substituent, we assume that 1 -methyl-4,4′-bi-pyridinium bromide is “activated” by a yet unknown light reaction.

Long-term clinical and radiological assessment of untreated severe cartilage damage in the knee: a natural history study

We aimed to evaluate whether and to what extent an isolated deep cartilage lesion localized within the tibiofemoral and the patellofemoral joint has an impact on the clinical outcomes and osteoarthritis (OA) progression when it is left untreated. From 1991 to 1994, 4121 consecutive knee arthroscopies were performed, and 37 of them in patients with a single isolated chondral lesion of Outerbridge grade 4 located within weight-bearing areas of the femoral and tibial condyles (FT group) and patella (P group). The lesion size ranged from 2 to 4 cm(2) . Outcomes were reported at a mean 15.3-year follow-up using the Lysholm score, the Tegner activity scale and the Womac score. The mean Lysholm, Tegner and Womac score in the FT group was 87.7, 5.6 and 88.7, respectively. In the P group, it was 83.8, 4.8 and 84.6, respectively (P<0.0.5). Osteoarthritic changes were found in 39% of the patients. There was no difference in OA severity between an injured and an uninjured knee. In patients of the FT group, there was a relationship between the incidence of tibiofemoral OA and patellofemoral OA (P=0.00075). Severe isolated single chondral damage left with no treatment has a limited influence on clinical outcomes and the development of OA.

Isolated full thickness chondral injuries. Prevalance and outcome of treatment. A retrospective study of 5233 knee arthroscopies

PURPOSE OF THE STUDY The aim of this study was to provide data on the prevalence and epidemiology of isolated deep chondral lesions of the knee, diagnosed in arthroscopy. The study was also aimed to analyse subjective treatment results of localized deep isolated cartilage lesions and to determine how the different factors might affect the final outcome. MATERIAL AND METHODS From 1997 to 2002, 5233 knee arthroscopies were performed. The first part of the study is an epidemiological and statistical analysis of the isolated articular cartilage lesions in which we used the questionnaire based on the International Knee Documentation Committee (IKDC) Questionnaire. The second part is the analysis of subjective treatment evaluation. For this purpose the IKDC criteria were used. Following aspects were taken into account: lesion location and size, time after surgery, patients' age, performed surgical cartilage procedure. The follow-up period ranged from 1 to 7 years. The statistical analysis was performed with the use of the Pearson correlation coefficient and t-test. Significance was set at p<0.05. RESULTS In the analyzed material cartilage lesion was diagnosed in 2931 patients (57.3%). Isolated localized chondral Outerbridge grade 3 and 4 lesions were documented in 5.2% of all patients with diagnosed cartilage lesion. The patellar articular surface (37.5%) and the medial femoral condyle (32.2%) were the most frequent localizations of these lesions. There was no correlation between the results and the period of time after arthroscopy. The best results were obtained in cases of loose body removal, debridement, mosaicplasty and also in cases where the lesion was left untreated. DISCUSSION The management of full-thickness cartilage injury remains one of the most difficult problems in the orthopedic surgery, particularly isolated and symptomatic. In 7 years of follow-up we found good and satisfactory results when debridement and loose body removal was performed and when the lesions was left untreated. Significantly the worst results in subjective evaluation we observed in marrow-stimulating procedures. This study confirms that the appropriate qualification for treatment plays the most important role in successive management of cartilage injuries. CONCLUSIONS Treatment of isolated deep chondral lesions of the knee remains a questionable issue. Little invasive arthroscopic methods as well as using no surgical treatment in grade 3 and 4 isolated cartilage lesions may be effective and improve symptoms and knee function at mid-term follow-up.Our data support also the contention that the natural history of cartilage lesions still remains unpredictable and not well understood.

Paraquat-Catalyzed Photodestructions in Subchloroplast Particles are Independent on Photosynthetic Electron Transport

Light dependent ethane formation and chlorophyll bleaching in isolated chloroplast lamellae are enhanced by either methylviologen or α-linolenic acid. Both ethane formation and chloro­phyll bleaching are also enhanced in chloroplast particles deficient in photosynthetic electron transport, e. g. after aging, heat treatment or digitonin fragmentation. Ethane formation by sub­ chloroplast particles from endogenous substrates in the presence of methylviologen is inhibited by superoxide dismutase or by a penicillamine copper complex exhibiting superoxide dismutase activity whereas chlorophyll bleaching is enhanced by superoxide dismutase - active substances.

Maximal rates of ethane formation in subchloroplast particles are observed when more than 50% of the chlorophyll is bleached and continues after 98% chlorophyll bleaching. This result indicated that methylviologen -stimulated ethane production in subchloroplast particles is not de­pendent on photosynthetic electron transport but involves “activated oxygen” - species like the superoxide radical ion, generated by a light receptor derived from the pigmentsystem of photo­ system I or activated after its destruction.