Short-term esmolol improves coronary artery remodeling in spontaneously hypertensive rats through increased nitric oxide bioavailability and superoxide dismutase activity.

The aim of this study was to assess the effects of short-term esmolol therapy on coronary artery structure and function and plasma oxidative stress in spontaneously hypertensive rats (SHR). For this purpose, 14-month-old male SHR were treated for 48 hours with esmolol (SHR-E, 300 µ g/kg/min). Age-matched untreated male SHR and Wistar Kyoto rats (WKY) were used as hypertensive and normotensive controls, respectively. At the end of intervention we performed a histological study to analyze coronary artery wall width (WW), wall-to-lumen ratio (W/L), and media cross-sectional area (MCSA). Dose-response curves for acetylcholine (ACh) and sodium nitroprusside were constructed. We also assessed several plasma oxidative stress biomarkers, namely, superoxide scavenging activity (SOSA), nitrites, and total antioxidant capacity (TAC). We observed a significant reduction in WW (P < 0.001), W/L (P < 0.05), and MCSA (P < 0.01) and improved endothelium-dependent relaxation (AUC(SHR-E) = 201.2 ± 33 versus AUC(SHR) = 97.5 ± 21, P < 0.05) in SHR-E compared with untreated SHR; no differences were observed for WW, MCSA, and endothelium-dependent relaxation by ACh at higher concentrations (10(-6) to 10(-4) mol/l) for SHR-E with respect to WKY. SOSA (P < 0.001) and nitrite (P < 0.01) values were significantly higher in SHR-E than in untreated SHR; however, TAC did not increase after treatment with esmolol. Esmolol improves early coronary artery remodeling in SHR.

Does the epiphyseal cartilage of the long bones have one or two ossification fronts?

Epiphyseal cartilage is hyaline cartilage tissue with a gelatinous texture, and it is responsible for the longitudinal growth of the long bones in birds and mammals. It is located between the epiphysis and the diaphysis. Epiphyseal cartilage also is called a growth plate or physis. It is protected by three bone components: the epiphysis, the bone bar of the perichondrial ring and the metaphysis. The epiphysis, which lies over the epiphyseal cartilage in the form a cupola, contains a juxtaposed bone plate that is near the epiphyseal cartilage and is in direct contact with the epiphyseal side of the epiphyseal cartilage. The germinal zone corresponds to a group of cells called chondrocytes. These chondrocytes belong to a group of chondral cells, which are distributed in rows and columns; this architecture is commonly known as a growth plate. The growth plate is responsible for endochondral bone growth. The aim of this study was to elucidate the causal relationship between the juxtaposed bone plate and epiphyseal cartilage in mammals. Our hypothesis is that cells from the germinal zone of the epiphyseal side of the epiphyseal cartilage are involved in forming a second ossification front that is responsible for the origin of the juxtaposed bone plate. We report the following: (a) The juxtaposed bone plate has a morphology and function that differs from that of the epiphyseal trabeculae; (b) on the epiphyseal edge of the epiphyseal cartilage, a new ossification front starts on the chondrocytes of the germinal area, which forms the juxtaposed bone plate. This ossification front is formed by chondrocytes from the germinal zone through a process of mineralisation and ossification, and (c) the process of mineralisation and ossification has a certain morphological analogy to the process of ossification in the metaphyseal cartilage of amphibians and differs from the endochondral ossification process in the metaphyseal side of the growth plate. The close relationship between the juxtaposed bone plate and the epiphyseal cartilage, in which the chondrocytes that migrate from the germinal area play an important role in the mineralisation and ossification process of the juxtaposed bone plate, supports the hypothesis of a new ossification front in the epiphyseal layer of the epiphyseal plate. This hypothesis has several implications: (a) epiphyseal cartilage is a morphological entity with two different ossification fronts and two different functions, (b) epiphyseal cartilage may be a morphological structure with three parts: perichondrial ring, metaphyseal ossification front or growth plate, and epiphyseal ossification front, (c) all disease (traumatic or dysplastic) that affects some of these parts can have an impact on the morphology of the epiphyseal region of the bone, (d) there is a certain analogy between metaphyseal cartilage in amphibians and mammalian epiphyseal cartilage, although the former is not responsible for bone growth, (e) comparative histological and anatomy studies are also warranted, to shed light on the phylogenetic study of epiphyseal cartilage throughout the changes that occur in the animal species.

Early regression of left ventricular hypertrophy after treatment with esmolol in an experimental rat model of primary hypertension.

Certain ß-adrenergic blockers have proven useful in the regression of ventricular remodeling when administered as long-term treatment. However, early regression of left ventricular hypertrophy (LVH) has not been reported, following short-term administration of these drugs. We tested the hypothesis that short-term administration of the cardioselective ß-blocker esmolol induces early regression of LVH in spontaneously hypertensive rats (SHR). Fourteen-month-old male SHRs were treated i.v. with vehicle (SHR) or esmolol (SHR-E) (300 µg kg(-1) min(-1)). Age-matched vehicle-treated male Wistar-Kyoto (WKY) rats served as controls. After 48 h, left ventricular morphology and function were assessed using M-mode echocardiograms (left ventricular mass index (LVMI), ejection fraction and transmitral Doppler (early-to-atrial filling velocity ratio (E/A), E-wave deceleration time (Edec time)). The standardized uptake value (SUV) was applied to evaluate FDG (2-deoxy-2[18F]fluoro-D-glucose) uptake by the heart using PET/CT. Left ventricular subendocardial and subepicardial biopsies were taken to analyze changes in cross-sectional area (CSA) of left ventricular cardiomyocytes and the fibrosis was expressed as collagen volume fraction (CVF). LVMI was lower in SHR-E with respect to SHR (P=0.009). There were no significant differences in EF, E/A ratio or Edec time in SHR-E compared with SHR (P=0.17, 0.55 and P=0.80, respectively). PET acquisitions in SHR-E showed lower (18)F-FDG uptake than SHR (P=0.003). Interestingly, there were no significant differences in SUV in either SHR-E or WKY (P=0.63). CSA in subendocardial and subepicardial regions was minor in SHR-E with respect to SHR (P<0.001), and there were no significant differences in CVF between both groups. Esmolol reverses early LVH in the SHR model of stable compensated ventricular hypertrophy. This is the first study to associate early regression of LVH with administration of a short-term ß-blocker.

Contribution to the initial pathodynamics of hip luxation in young rats.

BACKGROUND: An anatomo-functional system has been described for the normal hip of some young mammals. This system includes the ligamentum teres, the transverse acetabular ligament, and the meniscoid of the hip. PURPOSE: This report analyzes morphologic changes in the anatomo-functional system of young rats in an experimental model of hip luxation, and on the initial pathodynamics of luxation produced experimentally. METHODS: Hyperextension of the left knee was induced in 58 young rats through fixation of the tibia and femur with Kirschner wire. Radiographic, macroscopic, and microscopic parameters were analyzed for 3 study periods (group 1: 4 d, group 2: 1 wk, group 3: 2 wk), and macroscopic parameters were studied in a late group (group 4: 6 wk). RESULTS: Breaks in the Shenton line were observed from group 1 (subluxation) onward (luxation). Hypertrophy of the round and transverse acetabular ligaments of the acetabulum and meniscoid, progressive elevation of the meniscoid, and fibrosis of the fibrofatty (pulvinar) tissue occurred from group 1 onward. Radiographic and morphometric studies showed triplane innominate bone deformation (anterior bending, lateral tilt, and rotation of the ischium), which resulted in decreased joint space. As time progressed, the increase in these injuries was accompanied by morphologic changes in the acetabulum, posterosuperior displacement and reorientation of the acetabulum and extrusion of the femoral head. CONCLUSIONS: Under the conditions of this study, the temporospatial morphologic changes in the acetabulum due to injury of the anatomo-functional system, and the triplane pelvic deformity in the initial period of the injury, produced femoral head extrusion of the acetabulum. RELEVANT SYMPTOMS: These disorders may help us understand the pathogenic and clinical phenomena that appear in early stages of hip luxation disease.

Embryonic blastemic changes in retinoic acid-induced hindlimb deformity.

In this study we analyzed, on an experimental model, blastemic changes occurring during the embryonic period that may later cause fetal hindlimb deformity. Experimental induction of clubfoot-like deformity in rat fetuses was performed by maternal administration of retinoic acid (RA) (120 mg/kg body weight) as a single intragastric dose on day 10 of pregnancy (previous phase of this assay). The caudal and hindlimb blastemic changes were studied by mitosis count and stereological, immunohistochemistry and AgNOR techniques in the hindlimbs of 15-day embryos and in the caudal somites of 11-day embryos. In 15-day embryos from the assay group, hypoplasia and misorientation of hindlimbs were present in 90% of the cases. The histological study showed a blastemal defect as follows: (a) reduction in mesenchymal cell activity (mitotic and AgNOR activities); (b) increase of volume of vascular lumen; (c) reduction in volume of nerve structures, and (d) reduction in the percentage of pre-rhabdomyoblastic cells. In 11-day embryos from the assay group, caudal somites showed disruption, including loss of usual morphology. Moreover, somitic AgNOR activity decreased compared to the control group. The greatest reduction in the number of black-dots per cell was in the myotome. These findings suggest that a certain pathology of the somites, very little studied to date, might be involved in clubfoot pathogenesis.