Stage Of Hypertrophy Research Articles

CGMMV 감염시기가 수박과 오이의 생육 및 품질에 미치는 영향

CGMMV의 감염시기가 수박과 오이의 생육 및 품질에 미치는 영향을 조사하였다. 수박은 생육달계별로 영양생장기 (정식기, 경엽신장기 )와 생식생장기 (착과기, 과실비대기)로 구분하여 CGMMV를 접종하였고, 오이는 정식기와 첫 개화기에 각각 접종하여 피해해석을 실시하였다. 수박의 경우, 영양생장기에 감염되면 만장, 절간장, 엽면적, 과중이 크게 감소하였으나 생식생장기부터는 대조구와 완만한 차이를 보였다. 반면에 당도는 착과기 이전에 접종하면 무처리에 비해 낮았으나 과실비대기에 접종하면 큰 차이 가 없었다. 피수박 발생은 감염시기가 빠를수록 증가하는 경향이었다. 오이의 경우 초장은 접종시기별로 큰 차이는 없었으나 만장은 접종시기가 빠를수록 감소하였고 절간장과 엽수, 엾폭, 엽장도 같은 경향이었다. We investigated the effect of infection time of CGMMV on the growth and quality of watermelon and cucumber plants. The effect (damages by CGMMV) was estimated on the watermelon where CGMMV had been inoculated at different growth stages, vegetative (transplanting stage, vegetative growth stage) and reproductive growth stage (fruiting stage and fruit hypertrophy stage). In the case of cucumber, CGMMV was inoculated at transplanting stage and Erst flowering stage, respectively. When watermelon was infected with CGMMV at vegetative growth stage, vine length, internode length, leaf area, and fruit weight of the plants largely decreased compared with control plants, while the infected plant growth was not very different from control plants when it was infected at reproductive growth stage. Brix of the fruit of watermelon also decreased when the plants was infected with the virus earlier than fruiting stage. The occurrence of 'Pisubag', internal discoloration and decomposition of watermelon fruits, tended to be increased as earlier infection time with CGMMV In the case of cucumber infection time with CGMMV did not influence earlier growth of the plants, but did later growth showing that plant height, vine length, internode length, number of leaf, leaf wide, and leaf length of the plants decreased as infection time became to be earlier.

The effects of overexpression of the Na +/Ca 2+ exchanger on calcium regulation in hypertrophied mouse cardiac myocytes

In cardiac hypertrophy and failure it has been shown that the amount of Na/Ca exchanger protein can increase. Several studies have investigated this modification in overt heart failure. However, the role of Na/Ca exchanger overexpression during the development of hypertrophy is unknown. To address this question we investigated Ca 2+ regulation in an early stage of cardiac hypertrophy before signs of heart failure occurred and evaluated the role of Na/Ca exchanger overexpression. Cardiac hypertrophy was induced by a constant infusion of angiotensin II (Ang, 1 μg/min/kg) via an osmotic pump for 14 days. Thereafter, ventricular myocytes from either wild type (NON) or transgenic mice overexpressing the Na/Ca exchanger (TR) were isolated. Myocytes were loaded with indo-1 AM or fluo-4 AM to monitor cytoplasmic [Ca 2+] with all experiments performed at 37 °C. In myocytes exposed to Ang there was an increase in cell capacitance of more than 20% indicating cellular hypertrophy. Ca 2+ transients were prolonged in hypertrophied NON myocytes but not in TR myocytes. Action potentials had a less negative plateau in TR myocytes. Sarcoplasmic reticulum (SR) Ca 2+ content, measured using rapid caffeine application, was greater in TR myocytes but unaffected by hypertrophy. Ca 2+ spark frequency was significantly greater in TR. Na/Ca exchanger overexpression prevented the prolongation of the Ca 2+ transient observed in hypertrophy and maintained a similar SR Ca 2+ leak suggesting a compensatory role in Ca 2+ regulation in hypertrophied cardiac myocytes from transgenic mice. We suggest this compensatory effect is mediated by increased SR Ca 2+ content and faster Ca 2+ removal via the Na/Ca exchanger.

Coordinated shifts in Na/K-ATPase isoforms and their endogenous ligands during cardiac hypertrophy and failure in NaCl-sensitive hypertension.

NaCl loading of Dahl salt-sensitive rats (DS) stimulates marinobufagenin (MBG), an alpha1 Na/K-ATPase (NKA) isoform ligand. Cardiac function depends on NKA, which is regulated in part by endogenous digitalis-like ligands. Our goal was to study whether changes occur in MBG and endogenous ouabain (EO) production during cardiac remodelling in hypertensive DS, and whether these are associated with changes in myocardial NKA isoforms and sensitivity to MBG and ouabain. Changes in MBG and EO levels, changes in myocardial NKA isoform composition, and sensitivity to endogenous ligands during development of cardiac hypertrophy and the transition to heart failure were studied in DS rats with an 8% NaCl intake. The animals developed compensated left ventricular hypertrophy after 4 weeks, which progressed to heart failure at 9-12 weeks. The hypertrophic stage was associated with increased plasma MBG levels (mean +/- SEM of 1.22 +/- 0.22 versus 0.31 +/- 0.03 nmol/l; P < 0.01), increased sensitivity of NKA to MBG, and an increased abundance of alpha1 NKA. Plasma levels of EO did not change, and the sensitivity of NKA to ouabain decreased. The transition to heart failure was accompanied by a decrease in alpha1 NKA, a reduction in plasma MBG, and decreased sensitivity of NKA to MBG. In addition, an increased abundance of ouabain-sensitive alpha3 NKA, a three-fold rise in plasma EO (1.01 +/- 0.13 versus 0.27 +/- 0.06 nmol/l), and a seven-fold increase in the ouabain sensitivity of NKA compared with controls were observed. During cardiac hypertrophy and the transition to heart failure, a shift in endogenous NKA ligands production is linked to a shift in myocardial NKA isoforms.

Apoptosis of terminal hypertrophic chondrocytes in an in vitro model of endochondral ossification.

It is widely accepted that growth plate chondrocytes undergo apoptosis when they reach the terminal hypertrophic stage of their differentiation during the process of endochondral ossification in vivo. In this report, an established chondrocyte cell culture model of mammalian endochondral ossification was utilized to investigate the fate of chondrocytes after they had entered hypertrophy in vitro. Fetal bovine epiphyseal chondrocytes were treated with the demethylating agent, 5-azacytidine, for 48 h and then cultured under azacytidine-depleted conditions. There was evidence for apoptosis in azacytidine-treated cells, as demonstrated by nuclear condensation and fragmentation (days 27 and 35) using transmission electron microscopy, and the detection of exposed phosphatidylserine on the plasma membrane surface of apoptotic chondrocytes (day 27) using fluorescence-labelled annexin V. Treated cultures on days 10 and 20 and untreated cultures at all corresponding time-points showed no morphological characteristics of apoptosis. In situ hybridization studies of treated cultures revealed that expression of the apoptotic suppressor, bcl-2, remained consistently high throughout the culture period, whilst the apoptotic inducer, bax, was not expressed until day 23. Quantification of these data showed a gradual shift in the ratio of the expression level of bcl-2 and bax in favour of bax with time in culture, particularly from day 23 onwards. Taken together, the results indicate that azacytidine-treated epiphyseal chondrocytes entered terminal hypertrophy from day 23 onwards in culture and died by apoptosis. This study confirms this culture system as a successful recapitulation of the entire mammalian chondrocyte differentiation pathway, including apoptosis. The culture model will prove valuable for studies of the apoptotic fate of terminally differentiated chondrocytes in the growth plate with a view to providing a better understanding of the underlying mechanisms of skeletal malformations and other pathological disorders such as osteoarthritis.

CTGF/Hcs24, hypertrophic chondrocyte-specific gene product, interacts with perlecan in regulating the proliferation and differentiation of chondrocytes.

Connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) plays important roles in the control of the proliferation and differentiation of chondrocytes in vitro. To clarify the mechanisms of regulation by CTGF/Hcs24 with respect to cartilage metabolism, we investigated the interaction between CTGF/Hcs24 and heparan sulfate proteoglycan perlecan. An immunofluorescence study showed that CTGF/Hcs24 was colocalized with heparan sulfate and perlecan in human chondrosarcoma-derived chondrocytic cell line HCS-2/8 in vitro. Northern blot analysis showed that perlecan, syndecan-1, -2, and -4 transcripts were detected in HCS-2/8 cells. Particularly, expression of the perlecan gene increased markedly in HCS-2/8 cells by recombinant CTGF/Hcs24 (rCTGF/Hcs24) treatment. We also found that CTGF/Hcs24 interacted with perlecan from HCS-2/8 cells in vitro. Furthermore, CTGF/Hcs24-stimulated gene expression of the aggrecan gene, as well as DNA/proteoglycan synthesis, was diminished when HCS-2/8 cells were pretreated with heparinase, indicating that the effects of CTGF/Hcs24 on chondrocytes occurred through the interaction between CTGF/Hcs24 and heparan sulfate on the cells. An in vivo study using mouse growth plate revealed that CTGF/Hcs24 produced by hypertrophic chondrocytes was localized from the proliferative to the hypertrophic zone, whereas perlecan was predominantly localized in the prehyphertrophic zone. Consistent with such findings in vivo, the binding of (125)I-rCTGF/Hcs24 to maturing chondrocytes was at higher levels than that to chondrocytes in hypertrophic stages. These findings suggest that CTGF/Hcs24 produced in the hypertrophic region may act on chondrocytes in the proliferative and maturative zone via some heparan sulfate proteoglycan, such as perlecan.

Thyroid hormone enhances aggrecanase-2/ADAM-TS5 expression and proteoglycan degradation in growth plate cartilage.

Effects of thyroid hormone on proteoglycan degradation in various regions of cartilage were investigated. In propylthiouracil-treated rats with hypothyroidism, proteoglycan degradation in epiphyseal cartilage during endochondral ossification was markedly suppressed. However, injections of T(4) reversed this effect of propylthiouracil on proteoglycan degradation. In pig growth plate explants, T(3) also induced breakdown of proteoglycan. T(3) increased the release of aggrecan monomer and core protein from the explants into the medium. Accordingly, the level of aggrecan monomer remaining in the tissue decreased after T(3) treatment, and the monomer lost hyaluronic acid-binding capacity, suggesting that the cleavage site is in the interglobular domain. The aggrecan fragment released from the T(3)-exposed explants underwent cleavage at Glu(373)-Ala(374), the major aggrecanase-cleavage site. The stimulation of proteoglycan degradation by T(3) was less prominent in resting cartilage explants than in growth plate explants and was barely detectable in articular cartilage explants. Using rabbit growth plate chondrocyte cultures, we explored proteases that may be involved in T(3)-induced aggrecan degradation and found that T(3) enhanced the expression of aggrecanase-2/ADAM-TS5 (a disintegrin and a metalloproteinase domain with thrombospondin type I domains) mRNA, whereas we could not detect any enhancement of stromelysin, gelatinase, or collagenase activities or any aggrecanase-1/ADAM-TS4 mRNA expression. We also found that the aggrecanse-2 mRNA level, but not aggrecanase-1, increased at the hypertrophic stage during endochondral ossification. These findings suggest that aggrecanse-2/ADAM-TS5 is involved in aggrecan breakdown during endochondral ossification, and that thyroid hormone stimulates the aggrecan breakdown partly via the enhancement of aggrecanase-2/ADAM-TS5.

Characterization of cardiac hypertrophy and heart failure due to volume overload in the rat.

Alterations in general characteristics and morphology of the heart, as well as changes in hemodynamics, myosin heavy chain isoforms, and beta-adrenoceptor responsiveness, were determined in Sprague-Dawley rats at 1, 2, 4, 8, and 16 wk after aortocaval fistula (shunt) was induced by the needle technique. Three stages of cardiac hypertrophy due to volume overload were recognized during the 16-wk period. Developing hypertrophy occurred within the first 2 wk after aortocaval shunt was induced and was characterized by a rapid increase of cardiac mass in both left and right ventricles. Compensated hypertrophy occurred between 2 and 8 wk after aortocaval shunt where normal or mild depression in hemodynamic function was observed. Decompensated hypertrophy or heart failure occurred between 8 and 16 wk after aortocaval shunt and was characterized by circulatory congestion, decreased in vivo and in vitro cardiac function, and a shift in myosin heavy chain isozyme expression. However, the positive inotropic effect of isoproterenol was augmented at all times during the 16-wk period. Characterization of beta-adrenoceptor binding in failing hearts at 16 wk revealed a significant increase in beta(1)-receptor density, whereas beta(2)-receptor density was unchanged. Consistent with this, basal adenylyl cyclase activity was significantly increased, and both isoproterenol- and forskolin-stimulated adenylyl cyclase activities were also increased. These results indicate that upregulation of beta-adrenoceptor signal transduction is a unique feature of cardiac hypertrophy and failure induced by volume overload.

Interaction of AP-1 and the ctgf gene: a possible driver of chondrocyte hypertrophy in growth cartilage.

The expression of the connective tissue growth factor ( ctgf) gene increases along with the differentiation of growth cartilage cells, and the highest expression is observed in the hypertrophic stage. Similarly, recent reports demonstrated c- fos expression in chondrocytes in the early hypertrophic zone of growth cartilage, and suggested that the c- fos gene may play a crucial role in the regulation of hypertrophic differentiation. A chondrocytic human cell line, HCS-2/8, is known to retain a variety of chondrocytic phenotypes. When such cells were kept overconfluent, they expressed increasing levels of c- fos transcripts along a time course phenotypically similar to that of hypertrophic differentiation. Moreover, by using a competitive electromobility-shift assay, we found that AP-1, a Fos/Jun heterodimer, in HCS-2/8 was capable of binding not only to a typical AP-1-binding DNA fragment but also to the enhancer fragment of the ctgf gene. Based on the findings above, we hypothesize that, prior to hypertrophic differentiation, AP-1-related oncogenes are activated and that their gene products subsequently activate ctgf gene expression, which might eventually induce hypertrophy.

Vascular endothelial growth factor, capillarization, and function of the rat plantaris muscle at the onset of hypertrophy.

Capillary proliferation occurs during compensatory hypertrophy. We investigated whether the expression of vascular endothelial growth factor (VEGF) is elevated at the onset of hypertrophy when capillary proliferation is minimal, and whether muscle damage as assessed by muscle force deficits, may occur at the onset of hypertrophy. To investigate this, we induced in 9-month-old rats, under isoflurane anesthesia, hypertrophy of the left plantaris muscle by denervation of the gastrocnemius and soleus muscles. Capillarization was investigated in both the deep (oxidative) and the superficial (glycolytic) regions of the plantaris muscle. After 2 weeks, muscle mass had increased by 16% (p< 0.01), which was not accompanied by increases in fiber size. The maximal tetanic force (P(0)) and specific tension (P(0).g(-1) or P(0).cm(2)) and twitch characteristics were unaltered, and fatigue resistance of the overloaded muscle was improved (p< 0.05). However, the myosin heavy chain composition was unaltered. Capillary proliferation was not yet evident, but VEGF mRNA and protein levels were elevated 1.5- and 8-fold, respectively (p< 0.05). We concluded that the normal specific tension and the elevated VEGF expression after 2 weeks of overload indicate (1) an absence of or minimal muscle damage at this early time point, and (2) that elevated VEGF expression precedes and is involved in capillary proliferation that occurs during the later stages of compensatory hypertrophy.

Morphological and stereological characteristics of myocardial remodeling in aged spontaneously hypertensive SHR rats.

Myocardial remodeling in SHR rats with age-related hypertrophy was characterized by elimination of cardiomyocytes, their hypertrophy, and marked increase in the volume of the connective tissue. The count of cardiomyocytes with contracture injuries and subsegmental contractures increased, and pronounced perivascular and interstitial sclerosis developed in the hypertrophic myocardium of SHR rats. Damage to the microcirculatory bed manifested in degenerative changes and destruction of some endotheliocytes. Signs of atypical intracellular regeneration in myofibrils and impairment of their longitudinal orientation were revealed in cardiomyocytes in the late stage of compensatory hypertrophy.

The role of activating transcription factor-2 in skeletal growth control.

The growth plate is a dynamic area of cells that directs longitudinal bone growth and endochondral ossification by virtue of the progression of chondrocytes through the proliferation, maturation, and hypertrophic stages of cell differentiation. The initiation of growth-plate chondrocyte proliferation is stimulated by growth-hormone-induced IGF-1 1, followed by rapid clonal proliferation in response to a variety of growth factors. The chondrocytes exit the cell cycle after multiple cycles of proliferation to form a maturation, or prehypertrophic, zone. Here, chondrocytes sustain substantial increases in cell volume and, coincident with type-X collagen expression, mature to become hypertrophic chondrocytes. Mineralization of the cartilage matrix as well as vascular invasion, which introduces marrow and osteoblast precursors, occurs within the lowermost hypertrophic zone. Osteoblasts secrete bone matrix as well as proteases that break down the cartilage matrix. The hypertrophic chondrocytes undergo apoptosis, leaving behind osseous trabeculae that contribute to the microenvironment of the marrow. Both proliferation and hypertrophy are necessary for longitudinal bone growth 2. Proliferation initiates longitudinal growth and provides sufficient cells to undergo hypertrophy, while the large increase in cell diameter resulting from maturation and hypertrophy contributes substantially to bone length. Activating transcription factor-2 (ATF-2) is expressed only in the resting and proliferative zones of endochondral growth plates 3. Many studies, including our own, have suggested that ATF-2 has multiple roles in the control of skeletal growth 3-5 by virtue of its ability to control the expression of a variety of genes that promote or inhibit chondrocyte proliferation and growth-plate progression. Proliferation and cell-cycle exit are key events in the formation and maintenance of the growth plate. Proliferation is initiated in the G1 phase of the cycle, when mitogenic stimulation induces expression of D-type cyclins. D cyclins form complexes with cyclin-dependent kinases (CDKs) 4 and 6. CDK activity …

Differential induction of protein kinase C isoforms at the cardiac hypertrophy stage and congestive heart failure stage in Dahl salt-sensitive rats.

Several protein kinase C (PKC) isoforms may play important roles in cellular signaling pathways. Recent reports have suggested that PKC plays critical isoform-specific roles in the development of cardiac hypertrophy and heart failure. The purpose of the present study was to examine the expression profiles of PKC isoforms in models of cardiac hypertrophy and heart failure. We examined the cardiac expression of individual PKC isoforms at the cardiac hypertrophy stage and the heart failure stage in Dahl salt-sensitive rats by Western blot analysis. The levels of all PKC isoforms increased at the cardiac hypertrophy stage and the heart failure stage, but the pattern of increase differed among PKC isoforms at the heart failure stage. The expressions of PKCalpha, beta, and delta increased at the cardiac hypertrophy stage and remained elevated at the heart failure stage. On the other hand, the expression of PKCepsilon and atypical PKCs (aPKCs) increased at the cardiac hypertrophy stage, but this increase tended to decline at the congestive heart failure stage. These results suggest that there are two groups of PKC isoforms. Several reports have shown that PKCalpha, beta, and delta are involved in the development of cardiac hypertrophy and heart failure, and that PKCepsilon plays a role in the physiological hypertrophic responses and cardioprotective actions. These facts suggest that all PKC isoforms (PKCalpha, beta, delta, epsilon, and aPKCs) expressed in the heart may have similar functions at the cardiac hypertrophy stage, but that two groups of PKC isoforms (PKCalpha, beta, delta, and PKCepsilon, aPKCs) have different functions at the congestive heart failure stage.

Basic Helix-loop-helix Protein DEC1 Promotes Chondrocyte Differentiation at the Early and Terminal Stages

The mRNA level of basic helix-loop-helix transcription factor DEC1 (BHLHB2)/Stra13/Sharp2 was up-regulated during chondrocyte differentiation in cultures of ATDC5 cells and growth plate chondrocytes, and in growth plate cartilage in vivo. Forced expression of DEC1 in ATDC5 cells induced chondrogenic differentiation, and insulin increased this effect of DEC1 overexpression. Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) suppressed DEC1 expression and the differentiation of ATDC5 cells, but DEC1 overexpression antagonized this inhibitory action of PTH/PTHrP. Transforming growth factor-beta or bone morphogenetic protein-2, as well as insulin, induced DEC1 expression in ATDC5 cultures where it induced chondrogenic differentiation. In pellet cultures of bone marrow mesenchymal stem cells exposed to transforming growth factor-beta and insulin, DEC1 was induced at the earliest stage of chondrocyte differentiation and also at the hypertrophic stage. Overexpression of DEC1 in the mesenchymal cells induced the mRNA expressions of type II collagen, Indian hedgehog, and Runx2, as well as cartilage matrix accumulation; overexpression of DEC1 in growth plate chondrocytes at the prehypertrophic stage increased the mRNA levels of Indian hedgehog, Runx2, and type X collagen, and also increased alkaline phosphatase activity and mineralization. To our knowledge, DEC1 is the first transcription factor that can promote both chondrogenic differentiation and terminal differentiation.

Aminoguanidine inhibits mitogen-activated protein kinase and improves cardiac performance and cardiovascular remodeling in failing hearts of salt-sensitive hypertensive rats.

Congestive heart failure (CHF) is associated with inducible nitric oxide synthase (iNOS) expression in the failing human heart, and recently we have also demonstrated that iNOS expression was upregulated in Dahl salt-sensitive hypertensive (DS) rats with cardiac dysfunction and vascular remodeling. Thus, we evaluated whether aminoguanidine (AG), a selective iNOS inhibitor, protects against cardiac dysfunction and vascular remodeling in DS rats receiving a high-salt diet. AG (DSHF-AG, 150 mg/kg per day) or vehicle (DSHF-V) were given from left ventricular hypertrophy stage (11 weeks) to CHF stage (18 weeks) for 7 weeks. The left ventricular end-systolic pressure-volume relationship (contractility: E(es)) was measured by conductance catheter. Decreased E(es) in DSHF-V was significantly ameliorated by AG treatment. The iNOS mRNA and protein expression and phospho-p42/p44 extracellular signal-regulated kinase (ERK) activities in the left ventricle were significantly upregulated in DSHF-V compared with control rats, and significantly suppressed in DSHF-AG compared with DSHF-V. DSHF-V showed a significant increase of perivascular fibrosis and myocardial fibrosis, with all these parameters being significantly improved by AG treatment. We demonstrated that the selective iNOS inhibitor, AG, may be at least a potential therapeutic strategy for treating CHF and cardiovascular remodeling.

Critical role of Rho-kinase pathway for cardiac performance and remodeling in failing rat hearts.

Rho and Rho-kinase play a critical role in the regulation of cellular functions such as proliferation and migration. To elucidate the molecular mechanisms that regulate cardiac function and cardiovascular remodeling, we determined whether the signaling pathway through Rho is involved in Dahl salt-sensitive hypertensive rats with congestive heart failure (CHF) using a specific Rho-kinase inhibitor, Y-27632. Y-27632 was administered from the left ventricular hypertrophy stage (11 weeks) to the CHF stage (18 weeks) for 7 weeks. The left ventricular end-systolic pressure-volume relationship (contractility: E(es)) was evaluated using a conductance catheter. Downregulated E(es) in the CHF stage was significantly ameliorated by Y-27632 treatment. Increased RhoA protein, Rho-kinase gene expression and myosin light chain phosphorylations in CHF rats were suppressed by Y-27632. Upregulated proto-oncogene c-fos gene expression in CHF rats was decreased by inhibiting Rho-kinase. In contrast, Y-27632 showed no effect on upregulated extracellular signal-regulated kinases (ERK) and p70S6 kinase phosphorylations, which were reported to be involved in protein synthesis. In the CHF stage, Y-27632 effectively inhibited vascular lesion formation such as medial thickness and perivascular fibrosis. These results suggest that differential activation of the Rho-Rho-kinase and the ERK-p70S6 kinase pathways may play a critical role in CHF, and the Rho-Rho-kinase pathway is involved in the pathogenesis of cardiac dysfunction and cardiovascular remodeling. Thus, inhibition of the Rho-kinase pathway may be at least a potential therapeutic strategy for CHF.

Chondrocyte protein with a poly-proline region is a novel protein expressed by chondrocytes in vitro and in vivo

Chondrogenic differentiation is a multistep process entailing the sequential activation and inhibition of the expression of a number of genes. To identify genes preferentially expressed at the hypertrophic stage rather than early differentiation stages of chicken chondrocyte differentiation, a subtracted cDNA library was generated. Here we describe the characterization of a cDNA isolated from this library and that of the encoded protein referred to as Chondrocyte Protein with a Poly-proline Region (CHPPR). The cDNA coding for CHPPR hybridizes with a 3.0-kb mRNA expressed at extremely low levels in dedifferentiated chondrocytes, cultured in adherent conditions, at low levels in differentiating chondrocytes and at very high levels in hypertrophic chondrocytes in suspension culture. The Parathyroid Hormone peptide [PTH (1–34)] enhances accumulation of CHPPR mRNA in cultured chondrocytes. This 3.0-kb mRNA is also detectable in several chick embryo tissues but at a lower extent when compared to that present in cartilage and in hypertrophic chondrocytes. The CHPPR cDNA has a complete open reading frame coding for a polypeptide with a calculated mass of 35.6 kDa containing a proline-rich region with a PPLP motif (single-letter amino acid code). We demonstrate by Western blot analysis that two CHPPR isoforms are detected in the cell lysates from cultured chondrocytes when they are not in the culture medium; furthermore, we find that the CHPPR gene is expressed in vivo by chick embryo chondrocytes at higher levels in the prehypertrophic and hypertrophic zones.

Comparison of the effects of losartan and atenolol on common carotid artery intima-media thickness in patients with hypertension: results of a 2-year, double-blind, randomized, controlled study

Background: Hypertension induces progressive pathologic changes in the arterial wall. Experimental findings suggest that these changes, which include intima-media thickening, may be mediated, at least in part, by angiotensin II (AII).Objective: The Losartan Vascular Regression Study (LAARS) was a double-blind, parallel-group, randomized, controlled, multicenter study designed to compare the effects of the AII antagonist losartan and the beta-blocker atenolol on ultrasonographically determined intimamedia thickness (IMT) of the common carotid artery (CCA) in patients with mild to moderate essential hypertension.Methods: The primary end point of the study was the yearly rate of change (YRC) from baseline of the mean IMT of the CCA (CCA-IMTmean) averaged over 2 years of treatment. Secondary end points included IMT of the common femoral artery and sitting systolic and diastolic blood pressures (SiSBP/SiDBP). Safety assessments of losartan and atenolol were made by statistical and clinical review of the incidence of adverse experiences as well as review of vital signs and laboratory values. A total of 414 patients with essential hypertension were screened for study inclusion at 36 study centers in Germany and Brazil. Patients received losartan (50 mg once daily) or atenolol (50 mg once daily) for 24 months. Target blood pressure (SiSBP/SiDBP <140/<90 mm Hg) was achieved by adding hydrochlorothiazide 12.5 mg once daily, doubling the dose of study drug, or adding an open-label calcium channel blocker sequentially, as needed.Results: Of the original 414 patients screened, 280 hypertension patients (SiDBP 95–115 mm Hg), aged 35 to 65 years, with an IMT of 0.8 to 1.5 mm of the right or left CCA, were randomized to treatment with either losartan (n = 142) or atenolol (n = 138). Both losartan and atenolol therapy produced comparable reductions in CCA-IMTmean, over 24 months compared with baseline; the average YRC was −0.038 ± 0.004 mm/y (P ≤ 0.001) for losartan and −0.037 ± 0.004 mm/y (P ≤ 0.001) for atenolol. There were no significant differences between groups. Losartan showed a greater reduction of femoral artery IMT than did atenolol; the average YRC was −0.024 mm/y (P ≤ 0.05) for losartan and −0.017 mm/y for atenolol (P = NS), with no significant difference between groups. Both agents produced similar significant reductions in SiSBP and SiDBP and were generally well tolerated. Approximately 7% of losartan patients had drug-related clinical adverse events, compared with 12% of atenolol patients.Conclusions: The findings of LAARS, the first large study with an AII antagonist that examined IMT, suggest that AII antagonism reverses the early stages of vascular hypertrophy in patients with hypertension. Further studies are needed to delineate the relative importance of AII antagonism versus blood pressure reduction per se in mediating the beneficial vascular effects of losartan.

Betaxolol inhibits extracellular signal-regulated kinase and P70S6 kinase activities and gene expressions of platelet-derived growth factor A-chain and transforming growth factor-beta1 in Dahl salt-sensitive hypertensive rats.

We evaluated the protective effects of long-term treatment with betaxolol, a specific beta-antagonist, on platelet-derived growth factor (PDGF) A-chain and transforming growth factor (TGF)-beta1 gene expression in the left ventricle of Dahl salt-sensitive hypertensive rats fed a high-salt diet. In addition, we evaluated the relations between these effects and coronary microvascular remodeling, expression of extracellular signal-regulated kinases (ERK) belonging to one subfamily of mitogen-activated protein kinases, and expression of p70S6 kinase belonging to one subfamily of ribosomal S6 kinases. Betaxolol (0.9 mg/kg/day, subdepressor dose) was administered for 5 weeks, from 6 weeks of age to the left ventricular hypertrophy stage at 11 weeks of age. Increased PDGF A-chain and TGF-beta1 mRNA and protein expression were suppressed by betaxolol. Upregulated activities of ERK1/2 and p70S6 kinase phosphorylations were decreased by betaxolol. Betaxolol administration resulted in significant improvements in the wall-to-lumen ratio, perivascular fibrosis and myocardial fibrosis. Thus, we conclude that ERK1/2 and p70S6 kinase activities may play a key role in coronary microvascular remodeling of Dahl salt-sensitive hypertensive rats, and that beneficial effects of betaxolol on cardiovascular remodeling may be at least partially mediated by decreased PDGF A-chain and TGF-beta1 expression in the left ventricle.

Calcium handling and sarcoplasmic-reticular protein functions during heart-failure transition in ventricular myocardium from rats with hypertension

The objective of this study was to determine the primary event that occurs in Ca 2+-regulatory sarcoplasmic-reticular (SR) proteins during subacute transition from concentric/mechanically-compensated left ventricular (LV) hypertrophy to eccentric/decompensated hypertrophy. Using Dahl salt-sensitive rats with hypertension, changes of myocardial contraction, intracellular Ca 2+ transients, SR Ca 2+ uptake, protein levels of SR Ca 2+ ATPase (SERCA2), phospholamban, and calsequestrin (CSQ), and mRNA levels of SERCA2 and CSQ were serially determined and compared between the established stage of LV hypertrophy (LVH) and the subsequent stage of overt LV dysfunction (CHF). In LVH, isolated LV papillary muscle preparations showed an equal peak-tension level and a mild prolongation of the isometric tension decay compared to those of age-matched controls. The Ca 2+ transients as measured by aequorin were unchanged. The Ca 2+ uptake of isolated SR vesicles and the protein/mRNA levels of SR proteins were also equivalent to those of the controls. In contrast, in CHF, the failing myocardium showed a further prolongation of the contraction time course and a 39% reduction of the peak-tension development. The Ca 2+ transients showed changes consisting of a decrease in the peak level and a prolongation of the time course. In addition, the SR Ca 2+ uptake was decreased by 41%. Despite these functional changes, the protein and mRNA levels of the SR components remained equivalent to those of the age-matched controls. Thus, in this hypertensive animal, 1) at the LVH stage, myocardial contractility and intracellular capability to regulate Ca 2+ remained normal; 2) at the CHF stage, impaired SR Ca 2+ handling and the subsequent reduction of myocardial contraction were in progress; and 3) impairments of SR function occurred at the post-translational protein level rather than at the transcriptional/translational levels. Our findings support the role of SR proteins as the primary determinant of the contractile dysfunction that occurs during the heart-failure transition; however, post-translational modulators of these SR elements may also be critical.

Antioxidant changes in the hypertrophied heart due to energy metabolic disorder

Oxidative stress has been implicated in the pathogenesis of both heart hypertrophy and heart failure. Hypertrophied heart, in response to pressure overload, is associated with an increase in antioxidant capacity and a decrease in oxidative stress. However, in the hypertrophied heart due to energy metabolic disorder, antioxidant capacity has not been investigated. Antioxidant changes in juvenile visceral steatosis (JVS) mice, a model of heart hypertrophy due to disorder of fatty-acid oxidation, were examined at 4 weeks (developing hypertrophy stage) and 8 weeks of age (established hypertrophy stage). Superoxide dismutase activity in the JVS mice was higher than that in control mice at 4 weeks of age and was not different from that in the control mice at 8 weeks of age. Glutathione peroxidase activity in the JVS mice at 8 weeks of age was lower than that in the control mice. Catalase activity showed no significant differences between the control and the JVS mice. Lipid peroxidation in the JVS mice was significantly reduced at 4 weeks of age and increased toward control levels at 8 weeks of age. The levels of vitamin E in the heart were increased in the JVS mice at 8 weeks of age. To determine whether antioxidants affect the pathogenesis of hypertrophy in this model, long-term treatments of vitamin E and 2-mercaptopropionyl glycine were performed. Vitamin E treatment partially reduced the heart hypertrophy in these mice. The present study shows that heart hypertrophy in the JVS mice is accompanied with increased antioxidant capacity as indicated in other animal models of heart hypertrophy. The precise mechanism of heart hypertrophy in JVS mice is still unknown, but oxidative stress may play a role in the pathogenesis of heart hypertrophy.