Cloning of a Zoysia ZjLsL and its overexpression to induce axillary meristem initiation and tiller formation in Arabidopsis and bentgrass.

Zoysia grass and creeping bentgrass are important turf grasses used in parks, gardens and playing fields. Development of grasses with increased tiller formation will enhance their commercial cultivation. To investigate the regulatory mechanism of tiller formation, we cloned the Zoysia japonica Lateral suppressor-like (ZjLsL) gene. The Lateral suppressor (Ls) gene encodes a transcriptional regulator belonging to the plant-specific GRAS protein family of putative transcription factors, and regulates axillary meristem initiation. A full-length DNA of the ZjLsL gene was isolated by 5'/3' DNA walking. Phylogenetic analysis showed that ZjLsL is closely related to Ls genes. Southern blot analysis revealed that zoysia grass has two copies of the ZjLsL gene. ZjLsL expression was detected in all organs of zoysia grass but was most highly expressed in culms. Overexpression of ZjLsL in creeping bentgrass and Arabidopsis plants promoted axillary bud formation. These results suggest that ZjLsL plays an important role in axillary meristem initiation and tiller formation.

Exercise blood pressure and endothelial dysfunction in hypertension.

BACKGROUND: Hypertensive patients with persistent endothelial dysfunction have adverse cardiovascular prognosis. However, current methods aimed to assess endothelial dysfunction in those patients who possess clinical applicability. We hypothesised that such individuals could potentially be identified by an exaggerated systolic blood pressure (BP) response to a submaximal exercise. METHODS: We studied 22 male patients with essential hypertension who were categorised into two age-matched groups depending on their exercise systolic BP (ExSBP) rise during the 3-min exercise step test; the exaggerated ExSBP group [hyper-responders (> or = 40 mmHg)] and the low ExSBP responder group [hypo-responders (< or = 20 mmHg)]. Eleven healthy volunteers matched for age were used as control. Clinic and daytime ambulatory BP were assessed after 14 days of anti-hypertensive treatment withdrawal, which were not significantly different between groups. Vascular reactivity in response to intra-arterial infusions of acetylcholine, N(G)-monomethyl-l-arginine (l-NMMA) and sodium nitroprusside was assessed using forearm venous occlusion plethysmography. RESULTS: The hyper-responder group had significantly less forearm vasodilatation to acetylcholine compared with the hypo-responder group [percentage change in the forearm blood flow 125 (17) vs. 260 (28), mean (SEM); p < 0.001]. Similarly, the vasoconstrictive response to l-NMMA was significantly impaired in the hyper-responder group in comparison to the hypo-responder group [-30 (2) vs. -45 (4); p < 0.05]. In contrast, the vascular response to sodium nitroprusside was not different between groups suggesting preserved endothelial-independent vasodilatation. CONCLUSIONS: Despite similar ambulatory and office BP, the exaggerated ExSBP group had significantly worse endothelial function compared with the low ExSBP responder group. This simple and non-invasive test may be useful in routine clinical practice to aid risk stratification in hypertensive patients.

QT interval abnormalities are often present at diagnosis in diabetes and are better predictors of cardiac death than ankle brachial pressure index and autonomic function tests.

OBJECTIVES: To study serial measures of maximum QT interval corrected for heart rate (QTc) and QT dispersion (QTD) and their association with cardiac mortality patients with non-insulin dependent diabetes and to compare QT abnormalities with other mortality predictors (ankle brachial pressure index (ABPI) and autonomic function tests) in their ability to predict cardiac death. SETTING: Teaching hospital. METHODS AND PATIENTS: QT interval analysis, heart rate (RR) variation in response to deep breathing and standing, and ABPI were analysed in 192 patients with non-insulin dependent diabetes. Cardiac death was the primary end point. RESULTS: Mean (SD) follow up was 12.7 (3.2) years (range 1.2-17.1 years). There were 48 deaths, of which 26 were cardiac. QTc and QTD were individually significant predictors of cardiac mortality throughout the follow up period (p < 0.001). The predictability of QT parameters was superior to the predictability of ABPI and RR interval analysis. Temporal changes in QT parameters showed that the mean absolute QT parameter was a significant predictor of cardiac death (p < 0.001), whereas an intraindividual change in QT parameter over time was not predictive. CONCLUSION: QT abnormalities seem to exist at the point of diagnosis of diabetes and do not appear to change between then and the subsequent cardiac death. Furthermore, the analysis of QT interval is superior to ABPI and the RR interval in identifying diabetic patients at high risk of cardiac death.

Does a prolonged QT peak identify left ventricular hypertrophy in hypertension?

BACKGROUND: Left ventricular hypertrophy is a powerful predictor of death. Hypertensive subjects with left ventricular hypertrophy can have increased QT (end) dispersion, which is associated with cardiac death. Despite its prognostic value, QT (end) dispersion is not widely used. QTp (i.e. start of QRS to peak of T wave) is easier to measure. Therefore, we tested the hypothesis that long QT peak was associated with left ventricular hypertrophy and assessed its cost-effectiveness at diagnosing left ventricular hypertrophy. METHODS: ECGs and echocardiograms were recorded in 47 hypertensive patients. The onset of the QRS complex and peak of T wave of lead I of each subject's ECGs were digitised by one observer blind to results of the echocardiogram. Receiver-operator characteristics curves were plotted to determine the sensitivity and specificity of different cut-off values of QT peak at predicting left ventricular hypertrophy (defined as left ventricular mass index> or =134 g/m2 in male, > or =110 g/m2 in female). RESULTS: The heart-rate corrected QT peak of lead I correlated with left ventricular mass index (r=0.45, P=0.002). If all patients with a prolonged QT peak (> or =300 ms) had an echocardiogram, then no cases of left ventricular hypertrophy would be missed (100% sensitive). This novel ECG criterion not only had better positive and negative predictive values than the Sokolow-Lyon voltage criteria, but also resulted in more cost-effective resource use (< pound 370 vs. pound 1750/case of left ventricular hypertrophy detected). CONCLUSION: If the results of this small pilot study are confirmed in larger studies, then measuring QT peak of lead I may become a cost-effective way of identifying hypertensives who are likely to have echocardiographic left ventricular hypertrophy.

Reversible hypertension following coeliac disease treatment: the role of moderate hyperhomocysteinaemia and vascular endothelial dysfunction.

The vascular endothelium maintains a relatively vasodilated state via the release of nitric oxide (NO), a process that could be disrupted by hyperhomocysteinaemia. Since endothelial dysfunction is associated with increased systemic vascular resistance that is the hallmark of sustained arterial hypertension, we hypothesised that in patients with both hypertension and coeliac disease with hyperhomocysteinaemia (via malabsorption of essential cofactors), treatment of the latter disease could improve blood pressure (BP) control. A single patient with proven sustained hypertension and newly-diagnosed coeliac disease had baseline and post-treatment BP and endothelial function assessed by ambulatory BP monitoring (ABPM) and brachial artery forearm occlusion plethysmography respectively. This 49 year-old woman had uncomplicated sustained hypertension proven on repeated ABPM carried out 6 weeks apart (daytime mean 151/92 mm Hg and 155/95 mm Hg), and sub-clinical coeliac disease (gluten-sensitive enteropathy). Initial assessments revealed raised homocysteine levels with low normal vitamin B(12) level. It was likely that she had impaired absorption of essential cofactors for normal homocysteine metabolism. She adhered to a gluten-free diet and was give oral iron, folate and B(6) supplementations as well as B(12) injections for 3 months. Her BP had improved by 6 months and normalised by 15 months (daytime ABPM mean 128/80 mm Hg). There was parallel restoration of normal endothelial function with normalisation of her homocysteine levels. These observations suggest that sub-clinical coeliac disease related hyperhomocysteinaemia might cause endothelial dysfunction, potentially giving rise to a reversible form of hypertension. In addition, this case study supports the notion that irrespective of aetiology, endothelial dysfunction may be the precursor of hypertension. This highlights the need to resolve co-existing vascular risk factors in patients with hypertension.

Is aldosterone the missing link in refractory hypertension?: aldosterone-to-renin ratio as a marker of inappropriate aldosterone activity.

Use of the random aldosterone-to-renin ratio (ARR) as a reliable marker of inappropriate aldosterone activity has led to primary aldosteronism (PA) being increasingly diagnosed in hypertensive patients. At least 10% of hypertensives have been found to have PA, the majority of whom presumably have bilateral adrenal hyperplasia or idiopathic hyperaldosteronism as an aetiology for PA. Whilst these patients clearly have excess aldosterone activity, they have in common many features that are found in hypertensive patients in general, amongst which include heightened angiotensin II adrenal sensitivity. Whether these individuals belong within the spectrum of 'essential hypertension' is being debated, but is probably irrelevant clinically since they appear to respond favourably to spironolactone treatment. In addition, there is recent evidence suggesting that these patients overexpress a key enzyme involved in aldosterone production, the aldosterone synthase, the activity of which appears to relate to its genotypic variation.

Blood pressure determinants of left ventricular wall thickness and mass index in hypertension: comparing office, ambulatory and exercise blood pressures.

Left ventricular (LV) mass relates positively and continuously to cardiac mortality and thus its regression is a rational therapeutic aim. Whilst the office blood pressure (BP) relates poorly to LV mass, it was unclear whether the 24-h ambulatory BP or the exercise systolic BP (ExSBP) was the stronger correlate of LV structural indices. We studied 49 hypertensive patients with a mean age of 45 (s.d. 12) years with a mean body mass index of 27.1(3.9) kg/m(2). The mean (s.d.) of office BP, ambulatory BP and ExSBP measured at the end of the first three stages of Bruce protocol treadmill exercise I, II and III were 161(20)/99(10), 140(13)/89(10), 190(30), 198(30) and 201(33) mm Hg respectively. The LV indices measured echocardiographically were LV septal thickness (IVSd) (1.1(0.2) cm), LV posterior wall thickness (LVPWd) (1.0(0.1) cm) and LV mass indexed to body surface area (LVMI) (123(30) g/m(2)). Age and gender (male) had the highest correlations with the LV indices. Of the BP measures, the stage II ExSBP's correlation with the LV indices was consistently higher than all other ExSBP, office systolic BP and 24-h systolic ambulatory BP. In a stepwise multiple regression analysis on IVSd, after adjusting for age and gender, the stage II ExSBP was independently associated with IVSd (beta= 0.018 (s.e. 0.008), P = 0.024). When only BP measures were considered as explanatory variables only stage II ExSBP was a significant predictor (P = 0.0001) of IVSd as was the case with LVPWd (P = 0.006) and LVMI (P = 0.0008). Submaximal exercise BP measured at a workload comparable to physical activity encountered in daily life correlated more closely with the left ventricular wall thickness and mass. The exercise BP should perhaps be normalised in hypertension management to optimise regression of LV hypertrophy.

Nebivolol reverses endothelial dysfunction in essential hypertension: a randomized, double-blind, crossover study.

BACKGROUND: Vascular endothelial dysfunction may predict future atherosclerosis. Hence, an antihypertensive agent that reverses endothelial dysfunction and lowers blood pressure might improve the prognosis of patients with hypertension. We hypothesized that nebivolol, a vasodilating beta-blocker, could improve endothelial dysfunction. We tested this hypothesis by comparing the effects of nebivolol and atenolol on endothelial function. METHODS AND RESULTS: Twelve hypertensive patients with a mean ambulatory blood pressure of 154+/-7/97+/-10 mm Hg were randomized after a 2-week placebo run-in period (baseline) in a double-blind, crossover fashion to 8-week treatment periods with either 5 mg of nebivolol with 2.5 mg of bendrofluazide or 50 mg of atenolol with 2.5 mg of bendrofluazide. Forearm venous occlusion plethysmography and intra-arterial infusions of acetylcholine and N(G)-monomethyl-L-arginine (L-NMMA) were used to assess stimulated and basal endothelium-dependent nitric oxide release, respectively. Sodium nitroprusside was used as an endothelium-independent control. Nebivolol/bendrofluazide and atenolol/bendrofluazide each lowered the clinic blood pressure to the same extent (132+/-7/82+/-6 and 132+/-9/83+/-8 mm Hg, respectively; P<0.001 from baseline). The vasodilatory response to acetylcholine was significantly increased with nebivolol/bendrofluazide (maximum percentage change in forearm blood flow [mean+/-SEM], 435+/-27%, P<0.001) but not with atenolol/bendrofluazide. Similarly, the endothelium-dependent vasoconstrictive response to L-NMMA was significantly improved only with nebivolol treatment (percentage change in forearm blood flow, -54+/-5%; P<0.001). The response to sodium nitroprusside was not different between treatments, suggesting that the endothelium-independent pathway was unaffected. CONCLUSIONS: Nebivolol/bendrofluazide increased both stimulated and basal endothelial nitric oxide release, whereas for the same degree of blood pressure control, atenolol/bendrofluazide had no effect on nitric oxide bioactivity. Thus, nebivolol may offer additional vascular protection in treating hypertension.

Sugar-binding activity of pea lectin enhances heterologous infection of transgenic alfalfa plants by Rhizobium leguminosarum biovar viciae.

Transgenic alfalfa (Medicago sativa L. cv Regen) roots carrying genes encoding soybean lectin or pea (Pisum sativum) seed lectin (PSL) were inoculated with Bradyrhizobium japonicum or Rhizobium leguminosarum bv viciae, respectively, and their responses were compared with those of comparably inoculated control plants. We found that nodule-like structures formed on alfalfa roots only when the rhizobial strains produced Nod factor from the alfalfa-nodulating strain, Sinorhizobium meliloti. Uninfected nodule-like structures developed on the soybean lectin-transgenic plant roots at very low inoculum concentrations, but bona fide infection threads were not detected even when B. japonicum produced the appropriate S. meliloti Nod factor. In contrast, the PSL-transgenic plants were not only well nodulated but also exhibited infection thread formation in response to R. leguminosarum bv viciae, but only when the bacteria expressed the complete set of S. meliloti nod genes. A few nodules from the PSL-transgenic plant roots were even found to be colonized by R. leguminosarum bv viciae expressing S. meliloti nod genes, but the plants were yellow and senescent, indicating that nitrogen fixation did not take place. Exopolysaccharide appears to be absolutely required for both nodule development and infection thread formation because neither occurred in PSL-transgenic plant roots following inoculation with an Exo(-) R. leguminosarum bv viciae strain that produced S. meliloti Nod factor.

A review of the medical treatment of primary aldosteronism.

PURPOSE: Use of the aldosterone-to-renin ratio (ARR) has suggested that at least one in 10 hypertensive subjects have primary aldosteronism (PA). There is thus a timely need to review the literature for effective drug therapies and to speculate on other therapeutic options by taking into account recent advances in understanding of the PA disease pathophysiological process. DATA SOURCE: A MEDLINE and EMBASE search of all articles published from the start of the databases until July 1999 and reviews of the bibliographies of textbooks. STUDY SELECTION: Primary research articles on the medical treatment of PA with emphasis on diagnosis, treatment option, drug dosage, therapeutic response and adverse drug effect. DATA EXTRACTION: Study design and quality were assessed. Relevant data on diagnostic methodology, drug usage and response were analysed and compared. DATA SYNTHESIS: A select number of subjects with aldosterone-producing adenoma (APA) can be expected to respond well to surgical treatment For the majority of PA cases especially subjects with idiopathic hyperaldosteronism (IHA), long-term medical treatment is now safe and feasible although no randomized controlled trials have been carried out to date. The best therapeutic response is obtained by directly antagonizing aldosterone at the receptor level using medium to low dose spironolactone and this response can be predicted by a raised ARR. The response to other potassium-sparing diuretics and calcium channel blockers are modest. IHA responds better than angiotensin II-unresponsive APA to angiotensin converting enzyme inhibitors and this may also be true with angiotensin II receptor blockers. The discovery of the aldosterone synthase gene opens up the possibility for gene therapy. CONCLUSION: The diagnosis of PA allows appropriate management with resultant blood pressure control in many hypertensive subjects who otherwise have resistant hypertension despite multiple drug therapy.

Aldosterone to renin ratio as a determinant of exercise blood pressure response in hypertensive patients.

Aldosterone to renin ratio (ARR) is a marker of inappropriate aldosterone activity in hypertension. Since aldosterone may adversely affect vascular compliance, we hypothesised that the ARR would relate to exercise blood pressure (BP) responses in hypertension. Blood sampling was done in untreated hypertensives for plasma renin activity (PRA, ng/mL/hr) and plasma aldosterone (PA, pmol/L). ARR was derived by dividing the PA value by the PRA value, and this index was normalised by natural logarithm (lnARR) for further analyses. Each patient underwent 24-h ambulatory BP (ABP), and a 3-min submaximal exercise test using the Dundee Step Test. The Spearman rank correlation coefficients between lnARR and office BP (OBP), ABP and exercise BPs and BP changes estimated during exercise were assessed. A total of 119 (66 males) hypertensive subjects aged 48 (s.d. 12) years were studied. The respective OBP, ABP, exercise BP and the change in exercise BP were 167(23)/105(11), 140(15)/87(10), 189(26)/107(12) and 25(15)/2(9) mmHg. lnARR was significantly correlated with exercise systolic BP (r = 0.24, P < 0.001), exercise diastolic bp (r = 0.23, P < 0.05), systolic abp (r = 0.22, P < 0.05) and systolic obp (r = 0.19, P < 0.05). in a multiple regressional analysis controlling for age and sex and all other bp measurements to assess the relative strengths of correlation between all the bp indices with lnarr, only exercise systolic bp (P = 0.012) and the change in systolic BP during exercise (negatively, P = 0.013) emerged as significant independent predictors of lnARR. In conclusion, there was an independent and significant correlation between ARR and exercise systolic BP.

Exercise blood pressure correlates with the maximum heart rate corrected QT interval in hypertension.

Submaximal exercise systolic blood pressure (ExSBP) is a recognised predictor of cardiac mortality. This study examined the possibility that this might be related to increased QT dispersion or prolonged maximum QT(c) interval (QTcmax). Twenty-nine untreated hypertensive subjects were assessed. Each subject underwent an echocardiographic examination and a 24-h ambulatory blood pressure (ABP). ExSBP was measured during a 3-min lightweight submaximal Dundee step test. In multiple regressional analyses, only left ventricular mass index significantly predicted QT dispersion (R2 = 22.4%, P = 0.018) and QT(c) dispersion (R(2) = 25.3%, P = 0.012). However, with respect to QTcmax, ExSBP (R2 = 21.6%, P = 0.02) emerged as the sole significant predictor of this index. Five (17.2%) out of the 29 subjects had prolonged QTcmax > or = 430 ms and these subjects were not differentiated by 24-h ABP (146 (s.d. 21)/83 (16) vs 140 (14)/88 (11) mm Hg, P = Ns) but by ExSBP (226 (15) vs 188 (24) mm Hg, P = 0.002). In conclusion, systolic blood pressure measured during exercise correlated with QT(c) max in hypertension. This finding may partly explain the prognostic value of exercise blood pressure.

Adverse cardiac effects of salt with fludrocortisone in hypertension.

The effect of salt on blood pressure (BP) is controversial. A more important question is whether salt can produce cardiac target-organ damage, irrespective of its effect on BP. We assessed the effect of salt with fludrocortisone on QT dispersion and echocardiographic left ventricular diastolic function in a prospective interventional study involving 29 hypertensive subjects with a raised aldosterone/renin ratio who were hospitalized for investigation of possible primary aldosteronism. Each subject over 4 days was given a total of 28.8 g (480 mmol) of sodium chloride and 1.5 mg of fludrocortisone with potassium supplementation. Baseline and posttreatment 12-lead ECGs and echocardiograms were obtained. There were no significant changes in body weight, pulse rate, or BP after treatment with salt and fludrocortisone. Plasma sodium was significantly increased from 141.4 (SD 2.1) to 142.6 (SD 2.4) mmol/L (P:=0.001). QT and QTc dispersion both significantly increased: +19.6 (SD 16.5) ms (95% CI, 13.4 to 25.9) (P:<0.001) and +19.8 (SD 20.9) ms (95% CI, 11.8 to 27.7) (P:<0.001), respectively. There were no significant changes in (n=15) left ventricular dimensions or systolic function, but all diastolic filling indexes, including the preload-independent index, flow propagation velocity (55.49 [SD 10.91] to 48.96 [SD 11.40] cm/s, P:=0.018) worsened, suggesting significant deterioration of left ventricular diastolic function with salt and fludrocortisone. In conclusion, a combination of salt with fludrocortisone increased QT dispersion and impaired left ventricular diastolic relaxation in hypertensive patients with high aldosterone/renin ratios. This raises the possibility that salt may have BP-independent adverse cardiac effects in susceptible hypertensive subjects.

Effect of phenylephrine with and without atropine on QT dispersion in healthy normotensive men.

The present study examined if changes in cardiac after-load would affect QT interval dispersion. QT dispersion (QTd) on the 12-lead electrocardiogram is believed to be a noninvasive measure of electrical inhomogeneity in the heart and has recently been identified as a sensitive predictor of sudden cardiac death. In experimental models, an increase in cardiac afterload has been shown to alter action potential durations through mechanoelectrical feedback. This may result in an altered dispersion of action potential repolarization in the ventricle. Until now, there has been little evidence for this occurring in man in vivo. In the present study, the effects of afterload on QTd were examined in 10 healthy male volunteers (mean age [SD] 25 years [4.5]) who received an intravenous infusion of phenylephrine (0.2 to 3.6 microg/kg/min) given in incremental doses, and placebo in a blinded, crossover fashion. Because phenylephrine is known to alter heart rate (HR) significantly (via a reflex vagal response), the study was performed with and without atropine. We found a significant positive correlation between acute changes in blood pressure (BP) and changes in all QTd indexes (deltaQTd/delta systolic BP and deltaQTcd/deltasystolic BP r values 0.67 and 0.60, respectively; p <0.001). This relation was independent of HR changes or reflex vagal activity. Atropine had no significant effect on QTd. These observations have important clinical implications and may partly account for why sudden deaths and arrhythmic complications occur so frequently in conditions associated with increased after-load, such as hypertension and heart failure.