Biomedical subjects

Marina Politi Okoshi

Publications and source records attributed to Marina Politi Okoshi.

9 recordsLinked to original sources

PubMed2006

[Echocardiographic criteria for the definition of ventricular dysfunction severity in aortic banded rats].

OBJECTIVE: The purpose of this study was to identify echocardiographic parameters that allow distinguishing different levels of cardiac dysfunction in aortic banded rats. METHODS: Wistar male rats (90-100 g) were subjected to aortic banding (n=23) or a sham operation (n=12). The following echocardiographic parameters were evaluated and used to group rats into groups with similar characteristics using cluster analysis: absolute values and after normalization to body weight of left ventricular end-diastolic diameter (LVDD) and left atrial systolic diameter; left ventricular end-systolic diameter (LVSD); LV weight to body weight ratio (LVW/BW); three indexes of left ventricular shortening (endocardial fractional shortening, EFS; midwall FS, MFS; and posterior wall shortening velocity, (PWSV). RESULTS: The cluster analysis could group aortic banded rats into two groups: mild (n=13) and severe (n=9) stage of heart failure. There was no overlapping among the values of the 95% confidence interval of the following parameters between the two groups: LVDD, LVSD, EFS, MFS, LVW/BW, and PWSV. CONCLUSION: It is feasible to distinguish two groups of aortic banded rats according to the level of cardiac dysfunction using those echocardiographic parameters. This allows to perform longitudinal studies in homogeneous groups of rats with aortic banding and cardiac dysfunction.

Animals↗

PubMed2006

Heart failure alters matrix metalloproteinase gene expression and activity in rat skeletal muscle.

Heart failure is associated with a skeletal muscle myopathy with cellular and extracellular alterations. The hypothesis of this investigation is that extracellular changes may be associated with enhanced mRNA expression and activity of matrix metalloproteinases (MMP). We examined MMP mRNA expression and MMP activity in Soleus (SOL), extensor digitorum longus (EDL), and diaphragm (DIA) muscles of young Wistar rat with monocrotaline-induced heart failure. Rats injected with saline served as age-matched controls. MMP2 and MMP9 mRNA contents were determined by RT-PCR and MMP activity by electrophoresis in gelatin-containing polyacrylamide gels in the presence of SDS under non-reducing conditions. Heart failure increased MMP9 mRNA expression and activity in SOL, EDL and DIA and MMP2 mRNA expression in DIA. These results suggest that MMP changes may contribute to the skeletal muscle myopathy during heart failure.

Animals↗

PubMed2005

Myocardial dysfunction induced by food restriction is related to morphological damage in normotensive middle-aged rats.

Previous works from our laboratory have revealed that food restriction (FR) promotes discrete myocardial dysfunction in young rats. We examined the effects of FR on cardiac function, in vivo and in vitro, and ultrastructural changes in the heart of middle-aged rats. Twelve-month-old Wistar-Kyoto rats were fed a control (C) or restricted diet (daily intake reduced to 50% of the control group) for 90 days. Cardiac performance was studied by echocardiogram and in isolated left ventricular (LV) papillary muscle by isometric contraction in basal condition, after calcium chloride (5.2 mM) and beta-adrenergic stimulation with isoproterenol (10(-6) M). FR did not change left ventricular function, but increased time to peak tension, and decreased maximum rate of papillary muscle tension development. Inotropic maneuvers promoted similar effects in both groups. Ultrastructural alterations were seen in most FR rat muscle fibers and included, absence and/or disorganization of myofilaments and Z line, hyper-contracted myofibrils, polymorphic and swollen mitochondria with disorganized cristae, and a great quantity of collagen fibrils. In conclusion, cardiac muscle sensitivity to isoproterenol and elevation of extracellular calcium concentration is preserved in middle-aged FR rats. The intrinsic muscle performance depression might be related to morphological damage.

Aging↗

PubMed2004

Follow-up study of morphology and cardiac function in rats undergoing induction of supravalvular aortic stenosis.

OBJECTIVE: To characterize the follow-up of an experimental model of left ventricular hypertrophy (LVH) induced by supravalvular ascending aortic stenosis in young rats. METHODS: Wistar rats were submitted to thoracotomy and aortic stenosis was created by placing a clip on the ascending aorta (AoS group, n=12). Age-matched control animals underwent a sham operation (C group, n=12). Cardiac function was analysed by echocardiograms performed 6, 12, and 21 weeks after aortic banding. Myocardial morphological features and myocardial hydroxyproline concentration (HOP) were evaluated 2, 6, 12, and 21 weeks after surgery in additional animals. RESULTS: Aortic banding promoted early concentric LVH and a progressive increase in HOP. Under light microscopy, we observed myocyte hypertrophy and wall thickening of the intramural branches of the coronary arteries due to medial hypertrophy. Cardiac function was supranormal after 6 weeks (percentage of fractional shortening - EAo6: 70.3 +/- 10.8; C6: 61.3 +/- 5.4; p<0.05), and depressed in the last period. Diastolic dysfunction was detected after 12 weeks (ratio of early-to-late filling velocity - EAo12: 4.20 +/- 3.25; C12: 1.61 +/- 0.16; p<0.05). CONCLUSION: Ascending aortic stenosis promotes concentric LVH with myocardial fibrosis and minimal histological changes. According to the period of evaluation, cardiac function may be improved, normal, or depressed. The model is suitable and useful for studies on pathophysiology and treatment of the different phases of cardiac hypertrophy.

Analysis of Variance↗

PubMed2004

Improved systolic ventricular function with normal myocardial mechanics in compensated cardiac hypertrophy.

There is still controversy about the relation between changes in myocardial contractile function and global left ventricular (LV) performance during stable concentric hypertrophy. To clarify this, we analyzed LV function in vivo and myocardial mechanics in vitro in rats with pressure overload-induced cardiac hypertrophy. Male Wistar rats (70 g) underwent ascending aortic stenosis for 8 weeks (group AAS, n = 9). LV performance was assessed by transthoracic echocardiography under anesthesia. Myocardial function was studied in isolated papillary muscle preparations during isometric contraction. The data were compared with age- and sex-matched sham-operated rats (group C, n = 9). LV weight-to-body weight ratio (C: 2.13 +/- 0.14 mg/g; AAS: 3.24 +/- 0.44 mg/g), LV relative wall thickness (C: 0.18 +/- 0.02; AAS: 0.33 +/- 0.09), and LV fractional shortening (C: 54 +/- 5%; AAS: 70 +/- 8%) were increased in group AAS (P < 0.05). Echocardiographic analysis also indicated a significant association (r = 0.74; P < 0.001) between the percent fractional shortening index and LV relative wall thickness. The performance of AAS isolated muscle revealed that active tension (C: 6.6 +/- 1.7 g/mm2; AAS: 6.5 +/- 1.5 g/mm2) and maximum rate of tension development (C: 69 +/- 21 g/mm2/s; AAS: 69 +/- 18 g/mm2/s) were not significantly different from group C (P > 0.05). In conclusion, compensated pressure-overload myocardial hypertrophy is associated with preserved myocardial function and increased ventricular performance. The improved LV function might be due to the ventricular remodeling characterized by an increased relative wall thickness.

Animals↗

PubMed2003

Behavior of cardiac variables in animals exposed to cigarette smoke.

OBJECTIVE: To assess the behavior of cardiac variables in animals exposed to cigarette smoke. METHODS: Two groups of Wistar rats were studied as follows: control group (C), comprising 28 animals; and smoking group (S), comprising 23 animals exposed to cigarette smoke for 30 days. Left ventricular cardiac function was assessed in vivo with transthoracic echocardiography, and myocardial performance was analyzed in vitro in preparations of isolated left ventricular papillary muscle. The cardiac muscle was assessed in isometric contractions with an extracellular calcium concentration of 2.5 mmol/L. RESULTS: No statistical difference was observed in the values of the body variables of the rats and in the mechanical data obtained from the papillary muscle between the control and smoking groups. The values of left ventricular systolic diameter were significantly greater in the smoking animals than in the control animals (C=3.39 +/- 0.4 mm and S=3.71 +/- 0.51 mm, P=0.02). A significant reduction was observed in systolic shortening fraction (C=56.7 +/- 4.2% and S=53.5 +/- 5.3%, P=0.02) and in ejection fraction (C=0.92 +/- 0.02 and S=0.89 +/- 0.04, P=0.01). CONCLUSION: The rats exposed to cigarette smoke had a reduction in left ventricular systolic function, although their myocardial function was preserved.

Animals↗

PubMed2003

Ventricular remodeling induced by retinoic acid supplementation in adult rats.

Retinoic acid (RA) plays a role in regulating cardiac geometry and function throughout life. The aim of this study was to analyze the cardiac effects of RA in adult rats. Wistar rats were randomly allocated to a control group (n = 18) receiving standard rat chow and a group treated with RA (n = 14) receiving standard rat chow supplemented with RA for 90 days. All animals were evaluated by echocardiography, isolated papillary muscle function, and morphological studies. Whereas the RA-treated group developed an increase in both left ventricular (LV) mass and LV end-diastolic diameter, the ratio of LV wall thickness to LV end-diastolic diameter remained unchanged when compared with the control group. In the isolated papillary muscle preparation, RA treatment decreased the time to peak developed tension and increased the maximum velocity of isometric relengthening, indicating that systolic and diastolic function was improved. Although RA treatment produced an increase in myocyte cross-sectional area, the myocardial collagen volume fraction was similar to controls. Thus our study demonstrates that small physiological doses of RA induce ventricular remodeling resembling compensated volume-overload hypertrophy in rats.

Animals↗

PubMed2003

Myosin heavy chain expression and atrophy in rat skeletal muscle during transition from cardiac hypertrophy to heart failure.

The purpose of this investigation was to determine whether changes in myosin heavy chain (MHC) expression and atrophy in rat skeletal muscle are observed during transition from cardiac hypertrophy to chronic heart failure (CHF) induced by aortic stenosis (AS). AS and control animals were studied 12 and 18 weeks after surgery and when overt CHF had developed in AS animals, 28 weeks after the surgery. The following parameters were studied in the soleus muscle: muscle atrophy index (soleus weight/body weight), muscle fibre diameter and frequency and MHC expression. AS animals presented decreases in both MHC1 and type I fibres and increases in both MHC2a and type IIa fibres during late cardiac hypertrophy and CHF. Type IIa fibre atrophy occurred during CHF. In conclusion, our data demonstrate that skeletal muscle phenotype changes occur in both late cardiac hypertrophy and heart failure; this suggests that attention should be given to the fact that skeletal muscle phenotype changes occur prior to overt heart failure symptoms.

Animals↗

PubMed2002

Volume overload influence on hypertrophied myocardium function.

The aim of this study was to demonstrate that hypertrophied cardiac muscle is more sensitive to volume-overload than normal cardiac muscle. We assessed the mechanical function of isolated left ventricular papillary muscle from male spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) submitted to volume overload caused by aortocaval fistula (ACF) for 30 days. Muscles were perfused with Krebs-Henseleit solution at 28 degrees C and studied isometrically at a stimulation rate of 0.2 Hz. The ACF increased the right and left ventricular weight-to-body weight ratio in WKY rats; it also promoted right ventricular hypertrophy and further increased the basal hypertrophy in the left ventricle from SHR. The arterial systolic pressure was greater in SHR than in WKY rats, and decreased with ACF in both groups. Developed tension (DT) and maximum rate of DT (+dT/dt) were greater in the SHR-control than in the WKY-control (P < 0.05); the time from peak tension to 50% relaxation (RT 1/2) was similar in these animals. ACF did not change any parameters in the SHR group and increased the resting tension in the WKY group. However, the significant difference observed between myocardial contraction performance in WKY-controls and SHR-controls disappeared when the SHR-ACF and WKY-controls were compared. Furthermore, RT 1/2 increased significantly in the SHR-ACF in relation to the WKY-controls. In conclusion, the data lead us to infer that volume-overload for 30 days promotes more mechanical functional changes in hypertrophied muscle than in normal cardiac muscle.

Animals↗