bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in soil properties related to different land uses in part of the Nigerian semi‐arid Savannah
Authors: Jaiyeoba I.A.
Published: February 2007

Abstract. Changes in soil physical and chemical properties associated with different land uses including natural savannah were compared in Nigeria. The study was conducted on large unreplicated sites. There was a significant coarsening of texture, depletion of organic matter and nutrients and increase in bulk density under Eucalyptus camaldulensis and Mangifera indica (mango) plantations, and also under arable and fallow conditions compared with under natural vegetation. The soil conditions were slightly better under Mangifera than under Eucalyptus, and in the fallow land than the arable land and tree plantations, but the differences were mostly non‐significant. The land uses studied were less efficient than the natural savannah in protecting the soil from loss of organic matter and nutrients by offtake or surface washing. The options open to Nigerian smallholder fanners are discussed in relation to sustaining soil fertility and productivity.
Magnesium availability from kieserite and calcined magnesite on five soils of different pH
Authors: Heming S.D. , Hollis J.F.
Published: February 2007

Abstract. Five soils from the South of England were incubated with additions of magnesium fertilizers; two also received magnesian limestone. After two years, the recovery of the added magnesium by 0.5 h extraction with 1 m ammonium nitrate was 75–89% for kieserite granules, 64–84% for calcined magnesite powder (< 1 mm), but only 20–41% for calcined magnesite granules (1–3 mm) and 26–32% for ground magnesian limestone. These were all much greater than the Mg dissolved by extracting the fertilizers directly in 1 m ammonium nitrate.

In calcareous soils, recovery of Mg was less from the calcined magnesite but most of this reduction was due to its particle size rather than to soil pH.

The four magnesium sources are evaluated as fertilizers for agriculture. Kieserite is the most reliable means of raising low soil Mg status.
Loss of yield caused by soil erosion on sandy soils in the UK
Authors: Biot Y. , Lu X.X.
Published: February 2007

Abstract. Soil productivity, the intrinsic ability of land to yield useful products, can be affected by soil erosion. While much research has been carried out on the processes, there is as yet little information on the impact of soil erosion on in situ productivity of agricultural land in the British Isles.

This paper reports the results of a de‐surfacing experiment on deep sandy soils in East Anglia. Grain yields of fertilized barley planted immediately after de‐surfacing were at least 15 and 45% less on 15 and 25 cm de‐surfaced plots than on non‐desurfaced soils. There was strong evidence pointing to an acceleration of soil erosion itself on the de‐surfaced plots. Both the amount of water stored in the topsoil and water use by the crop decreased with increasing severity of simulated erosion. We observed a drop in organic matter and readily available nitrogen with erosion. Nitrogen mineralization and leaching losses were also affected by simulated soil erosion.

The experiment showed that sudden severe erosion may induce substantial barley production losses on deep sandy soils. The size and effect of de‐surfacing depends on a number of factors such as soil depth, subsoil type, precipitation and crop type.
Sewage sludge as a fertilizer of pole stage forests: short‐term hydrochemical fluxes and foliar response
Authors: Ferrier R.C. , Edward A.C. , Dutch J. , Wolstenholme R. , Mitchell D.S.
Published: February 2007

Abstract. Proposed restrictions on the disposal of sewage to the marine environment means that alternative land based outlets are required in the UK. Commercial forestry represents a significant land use that could receive and benefit from the application of sewage sludge, to overcome the generally poor soil nutrient status. The oligotrophic and sensitive nature of surface waters in many afforested areas requires that the environmental consequences of the widespread use of organic fertilizers in forestry are carefully considered. This paper compares the effects of an N and P fertilizer with that of sewage sludge on the nutrient content of foliage in a pole stage Scots pine (Pinus sylvestris) forest and of nutrient fluxes in soil. Both conventional fertilizer and sewage treatments had significant but differing effects on the availability and leaching of the major nutrients, especially N and P. Evidence for increased nitrification and nitrate production with time was apparent for both treatments. Fluxes of N and P in mineral horizon leachate were consistently smaller than those from the overlying organic horizon. Foliar nutrient concentrations after one year were significantly higher (P < 0.01) in all of the treatments, and conventional fertilization with urea produced a significantly higher foliar N concentration than that measured in the sludge‐treated plots. There was no evidence for appreciable N or P leaching from the site within a year of sludge application.
Field measurement of time to ponding
Authors: Kumke T. , Mullins C. E.
Published: February 2007

Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double‐ring infiltrometers and tensiometers, respectively, on two sandy loams in north‐east Scotland. The time to ponding for constant‐rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (‐2 to ‐ 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation.
Infiltration rates, surface runoff, and soil loss as influenced by grazing pressure in the Ethiopian highlands
Authors: Mwendera E. J. , Saleem M. A. Mohamed
Published: February 2007

Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal‐unit‐months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing ‘slope‐specific’ grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long‐term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.
Practice to avoid contamination of drainflow and runoff from slurry spreading in spring
Authors: Parkes M. E. , Campbell J. , Vinten A. J. A.
Published: February 2007

Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The ‘mobile water’ pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted ‘mobile water’ pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH4+ ‐N occurred under ‘bypass flow’ conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m3/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well‐drained, partially frozen ground to avoid compaction by slurry tankers.
Phosphorus sorption capacities and saturation of soils in two regions with different livestock densities in northwest Germany
Authors: Leinweber P. , Lünsmann F. , Eckhardt K. U.
Published: February 2007

Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H2O‐P), by double lactate (DL‐P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle‐catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.

The mean concentrations of H2O‐P (0.4mmol/kg) and DL‐P (3.9 mmol/kg) were lower in the Harle‐catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate‐extractable Al (Alox) and Fe (Feox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate‐extractable P (Pox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in Pox could be explained by the routinely determined H2O‐Por DL‐P. Geostatistical analyses indicated that the spatial variability of Pox depended on manurial history of fields and Alox, showed still smaller‐scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P‐test values, digital maps and geostatistical methods.
The factors limiting crop production on the Mubangwe Farm, Malawi
Authors: Matabwa C. J. , Rowell D. L.
Published: February 2007

Abstract. Mubangwe Farm, northern Malawi, was brought into cultivation from savanna vegetation with Brachystegia between 1970 and 1983 to produce tobacco, maize and groundnuts. Because of poor yields even with inputs of lime, N, P and K the fields were soon abandoned. The soils were only moderately acidic with little likelihood of Al toxicity. They held only small amounts of exchangeable Ca2+ (down to 0.01 cmolc/kg) particularly at depth. Phosphorus availability was low particularly in the subsoil. A minus‐one pot experiment showed that the growth of sorghum in topsoil samples was limited by lack of N, P, S and Ca. The lower availabilities of P and Ca in the subsoil are therefore likely to be major limitations to growth, allowing only limited root penetration. The loamy sand to sandy clay soils generally had small available water capacities (down to 0.07 cm3/cm3) which, with restricted root development, may have lead to drought in dry periods during the growing season. The findings emphasize the need to measure both subsoil and topsoil properties when new areas of land are being developed for crop production.
Straw incorporation and immobilization of spring‐applied nitrogen
Authors: Bhogal A. , Young S. D. , Sylvester‐Bradley R.
Published: February 2007

Abstract. The effect of rate and timing of autumn/winter straw incorporation on the immobilization of spring‐applied N‐fertilizer are studied. The immobilization of 15N‐labelled fertilizer by straw was determined in pot trials with a sandy loam soil (Wick series) collected from two field experiments. In experiment 1, straw was incorporated at four different rates in the autumn; experiment 2 had a fixed rate of straw (7.5 t/ha) incorporated at monthly intervals from September to March. Immobilization in spring was not enhanced when only stubble was incorporated in autumn. However, autumn incorporation of 7.5 t/ha straw resulted in a significant increase in the immobilization of spring‐applied N, equivalent to 10 kg/ha; when 15 t/ha straw was incorporated, immobilization increased to 18 kg/ha. The enhancement of immobilization, immediately following fertilizer application, was dependent on the extent of straw decomposition prior to N application. Thus immobilization was related to cumulative thermal time (day °C above 0°C; Tsum between the date of straw incorporation and fertilizer application). Straw which had been incorporated for Tsum > 1200 no longer caused appreciable immobilization of spring fertilizer.
Chemical extractability and availability of heavy metals after seven years application of organic wastes to a citrus soil
Authors: Canet R. , Pomares F. , Tarazona F.
Published: February 2007

Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0‐20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water‐soluble plus exchangeable, organically bound, carbonate‐associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water‐soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.
Dynamic model for the effects of K‐fertilizer on crop growth, K‐uptake and soil‐K in arable cropping. 1. Description of the model
Authors: Greenwood D. J. , Karpinets T. V.
Published: February 2007

Abstract. To provide a practical aid to improving fertilizer practice a mechanistic model was developed that can be readily calibrated for widely different crops. Most of the inputs are easy to obtain and the others, the amounts of fixed soil‐K and the velocity constants for fixation and release of soil‐K, can be readily measured by a novel procedure which is described.

The model calculates for each day the potential increase in plant weight and the increment in root length, from the current plant mass, its %K and pan evaporation. It calculates the maximum amount of K that could be transported through soil to the root surfaces. It modifies this potential uptake by taking account of the ‘feedback’ of plant K on root absorption to give the actual uptake and a new %K in the plant. It calculates the radii of the depletion zones around each root increment and the interchange between the solution, exchangeable and fixed‐K in these zones and also in the undepleted regions of soil. Routines are included for the effects of weather on the various processes. Differences between species are accommodated by selecting one of three algorithms for root growth and by adjusting the values of two crop‐K parameters that define the decline in a critical and a maximum possible %K with increase in plant mass per unit area.

A simplified version of the model runs interactively on the Internet at: http://www.qpais.co.uk/moda‐djg/potass.htm
The influence of sub‐optimal irrigation and drought on crop yield, N uptake and risk of N leaching from sugarbeet
Authors: Groves S. J. , Bailey R. J.
Published: February 2007

Abstract. Variously timed sub‐optimal irrigation strategies were applied to sugarbeet grown on a light soil (loamy sand or sandy loam) over four seasons (1991 to 1994) to investigate the effect on crop growth and nitrate leaching risk. Data from the two dry seasons, (1991 and 1994) are reported here. In the driest year (1991) soil mineral N levels after autumn harvest were negatively related to crop water use (P < 0.05). In this season, there was little drainage from the soil profile, and full irrigation reduced residual soil N by 31 kg N/ha (0‐90 cm) compared with the unirrigated treatment (79 kg N/ha). The potential for N leaching during the ensuing winter was consequently more than halved. In 1991 and 1994 there was a strong positive linear relationship between dry matter yield, N uptake and water use, but a negative relationship between plant N concentration and water use. These relationships were a function of the severity and not the timing of drought. The additional N uptake associated with increased irrigation and crop water use was biased towards a large concentration in the aboveground crop (tops), which are normally returned to the soil. The C:N ratio of sugarbeet tops was affected by crop water supply with droughted crops having lower values. This would also influence N release and subsequent leaching risk. However, the effects of drought on N leaching risk were relatively small when compared with other root crops such as potatoes.
Constructing a nitrogen fertilizer recommendation system using a dynamic model: what do farmers want?
Authors: Smith J. U. , Dailey A. G. , Glendining M. J. , Bradbury N. J. , Addiscott T. M. , Smith P. , Bide A. , Boothroyd D. , Brown E. , Cartwright R. , Chorley R. , Cook S. , Cousins S. , Draper S. , Dunn M. , Fisher A. , Griffith P. , Hayes C. , Lock A. , Lord S. , Mackay J. , Malone C. , Mitchell D. , Nettleton D. , Nicholls D. , Overman H. , Purslow J. , Scholey A. , Senior S. , Sim L. , Taylor P.
Published: February 2007

Abstract. An effective fertilizer recommendation system requires information on seasonal, soil‐related and cultural variations in soil mineral nitrogen (N) and nutrient requirements of the crop. This can be provided by dynamic N turnover models, such as listed by Plentinger & Penning De Vries (1996). In this paper, we describe a survey of farmer opinion designed to ascertain what farmers want from such a decision support system. Over 100 farmers were surveyed. Surveyed farmers requested that default values be available for all model inputs. Inputs should be entered both by windows‐based menu (for clarity) and tabular format (for speed), have user‐selected units, and be fully supported by context‐sensitive help. The system should have a hierarchical structure allowing access to fixed parameters, and be compatible with commonly used farm recording packages. Recommendations should be provided both for the field (single and optional application rates), and in tabular format across the whole farm. Simulations should be easily rerun using more recent crop and weather data. Turnover processes underlying recommendations should be illustrated by flow diagrams of flux between pools, pie charts of fertilizer fate, bar charts of movement down the soil profile and graphical plots of changes in N status against time.
Fluxes of methane from rice fields and potential for mitigation
Authors: Neue H. U.
Published: February 2007

Abstract. Methane (CH4) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH4; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH4 emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH4 fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH4 emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade‐offs that are possible, have still to be identified.
A simple method for estimating nitrate removal from floodwaters in river marginal wetlands
Authors: Maltby E. , Jewkes E. C. , Baker C. J. , Mockler N. J. , Flynn N. , Gardner P. J.
Published: February 2007

Abstract. Soil cores from river marginal wetlands in the UK, France and Ireland, sampled and contained within PVC piping, were flooded with nitrate‐N enriched water. Half of the cores were sterilized prior to flooding to destroy the denitrifying bacteria. The change in nitrate‐N concentration in the floodwater was measured over time. It is argued that the observed nitrate depletion rates (from 0.4 to 2.3 kg/ha per day) may be identified With microbially‐mediated denitrification. The results show the method to be a simple and direct procedure for the assessment of spatial variation in nitrate‐sink capacity. The depth of the denitrifying layer at the soil‐water interface was confirmed to be of the order of a few mm.
Observations on the spatial and temporal variation in the phosphorus status of lakes in the British Isles
Authors: Foy R. H. , Bailey‐Watts A. E.
Published: February 2007

Abstract. An examination of total phosphorus (TP) concentrations from 902 lakes in England, Scotland and Northern Ireland (NI), suggest that only Scottish lakes have a high percentage (73%) of oligotrophic waters (TP<10 μg PI‐1). The TP status of upland lakes in NI was greater than Scottish lakes particularly if lake catchments were afforested. Although lowland lakes in NI drain a predominately non‐urbanized landscape, 38% of lakes below 100 m had TP concentrations > 100 μg PI‐1 and only 29% <35 μg PI‐1. English lakes tended to have higher TP concentrations (70% > 101 μg PI‐1) which may reflect P inputs from sewage treatment works (STWs) although lakes draining agricultural catchments frequently produced high TP concentrations. Between 1985 and 1995, annual point source TP inputs to Loch Leven, Scotland, declined by 8 tonnes P or 40% of the 1985 TP loadings to the Loch. As point source inputs were proportionally richer in dissolved molybdate reactive phosphorus (MRP) than diffuse inputs, the MRP loading was reduced by 46%. From 1974 to 1995, TP concentrations in Lough Neagh (NI) increased despite reduced TP inputs from STWs. Partitioning of annual TP loadings from two major inflowing rivers to Lough Neagh, showed river MRP loadings from non‐point sources had been increasing at annual rates of 1.9 and 2.3 kg P km‐2. The remaining non‐MRP river loadings had not been influenced by lower TP loads from STWs and showed no tendency to increase with time. Insufficient data is available from other lake systems in the British Isles to judge whether the increase in non‐point source MRP loadings observed in the Lough Neagh catchment has been repeated elsewhere.
Effect of Fixed‐Dose ACE‐Inhibitor/Calcium Channel Blocker Combination Therapy vs. ACE‐Inhibitor Monotherapy on Arterial Compliance in Hypertensive Patients With Type 2 Diabetes
Authors: Winer Nathaniel , Folker Amy , Murphy Julie A. , Hung Elena , Bard Mara , Perkelvald Alexander , Sowers James R. , Bakris George L.
Published: February 2007

Assessment of vascular compliance may be a useful measurement of the clinical effects of antihypertensive treatment. Both angiotensin‐converting enzyme (ACE) inhibitors and calcium channel blockers are known to improve vascular elasticity. A study was performed to test the hypothesis that combined therapy with an ACE inhibitor and a calcium channel blocker would have additive benefits on vascular compliance at similar levels of blood pressure (BP), as compared with monotherapy with an ACE inhibitor. This 12‐week, double‐blind study was a substudy of a larger clinical hypertension study conducted in patients with hypertension and type 2 diabetes. Subjects (N=20) were randomized to either a fixed‐dose combination of amlodipine besylate/benazepril HCl or to enalapril monotherapy. BP, heart rate, large‐ and small‐vessel compliance, systemic vascular resistance, and urinary microalbumin excretion were assessed at baseline and after treatment. Both treatments were similarly effective in lowering BP, reducing systemic vascular resistance, and decreasing urinary microalbumin excretion. Improvement in large‐vessel compliance was significantly greater among subjects who received ACE‐inhibitor/calcium channel blocker combination therapy (52%) as compared with those who received ACE‐inhibitor monotherapy (32%;

p

<0.05). No significant change in small‐vessel compliance was observed with either treatment. Greater improvement in large‐vessel compliance with combination therapy was independent of BP lowering.
Dietary Protein Type and Cardiovascular Disease Risk Factors
Authors: Vega‐López Sonia , Lichtenstein Alice H.
Published: February 2007

Observational studies suggested a negative association between vegetable protein and cardiovascular disease risk, whereas intervention studies have been less consistent. The majority of interventional studies that have evaluated the effects of soy protein compared to animal protein have used casein. Relative to casein, the effect of soy protein on lipids and lipoprotein appears to be variable and less dramatic than originally reported. When compared to animal proteins other than casein, relatively large intakes of soy protein (≥25 g/d) appear to have a consistent, albeit small (5%), hypocholesterolemic effect. When assessed, no consistent additional benefit of soy protein on other cardiovascular disease risk factors; Lp(a), inflammatory markers, biomarkers of oxidative stress and endothelial function, has been reported. The data available on the effect of dietary protein on plasma lipids, lipoprotein levels, and cardiovascular disease risk factors is difficult to interpret and insufficient to account for the discrepancy between the observational and interventional studies.
Adverse Events With Concomitant Amiodarone and Statin Therapy
Authors: Alsheikh‐Ali Alawi A. , Karas Richard H.
Published: February 2007

The authors reviewed adverse events (AEs) reported to the United States Food and Drug Administration to determine the percentage of statin‐associated AE reports with concurrent amiodarone use for simvastatin, atorvastatin, and pravastatin. AEs affecting the following organ systems were analyzed: muscle, liver, pancreas, and bone marrow. The percentage of simvastatin reports with concurrent amiodarone use was 1.0%, compared with 0.7% of the atorvastatin‐ associated reports (p=not significant). The percentage of pravastatin reports with concurrent amiodarone use was 0.4% (p<0.05 for pravastatin vs. simvastatin). Muscle toxicity was the most commonly reported statin‐amiodarone AE, accounting for 77% of the reports. AEs tended to occur in older male patients (mean age, 76 years), who were on multiple other medications (mean number of other medications, five). Clinicians should be vigilant about muscle‐related complaints in patients concomitantly taking amiodarone, especially in elderly patients on multiple medications. Use of a statin not metabolized through the cytochrome P450–3A4 system may be appropriate in this setting.
Non‐High‐Density Lipoprotein Cholesterol: Why Lower Is Better
Authors: Garg Rahul , Vasamreddy Chandrasekhar R. , Blumenthal Roger S.
Published: February 2007

Recent comparative trials of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitors (statins) suggest that lower is better and that reducing low‐density lipoprotein cholesterol (LDL‐C) levels to below 100 mg/dL can provide additional clinical benefit. Non‐high‐density lipoprotein cholesterol (non‐HDL‐C) contains more atherogenic cholesterol than LDL‐C and is considered a more accurate measurement of the total amount of atherogenic particles in the circulation. Therefore, the principle that “lower is better” may also apply to lowering levels of non‐HDL‐C. In persons with high triglycerides (200–499 mg/dL), LDL‐C remains the primary target of therapy, but non‐HDL‐C is an important secondary therapeutic target. Non‐HDL‐C is strongly correlated with small dense LDL as well as apolipoprotein B, an established predictor of cardiovascular disease risk. Current evidence indicates that statins not only rapidly and dramatically reduce LDL‐C, but also have a similar effect on non‐HDL‐C, and that the greater the reduction in LDL‐C, the greater will be the reduction in non‐HDL‐C.
Do the Metabolic Effects of β Blockers Make Them Leading or Supporting Antihypertensive Agents in the Treatment of Hypertension?
Authors: Sarafidis Panteleimon A. , Bakris George L.
Published: February 2007

Reduction of blood pressure to guideline goals (i.e., <130/80 mm Hg) in persons with diabetes is crucial to optimally reduce cardiovascular events and kidney disease progression. Since many patients will be >20/10 mm Hg above this goal, most guidelines recommend using agents that block the renin–angiotensin system in concert with a thiazide‐like diuretic to achieve goal blood pressure. Meta‐analyses of clinical trials indicate that while all classes of antihypertensive agents reduce cardiovascular risk, they exert different effects on glucose utilization and lipids and, hence, may affect morbidity. Specifically, β blockers, in general, worsen insulin resistance and increase triglycerides in a dose‐dependent fashion. Moreover, they are not recommended as initial therapy for hypertension treatment in the absence of heart failure or recent myocardial infarction, especially in the elderly. Recent studies support the notion that newer β blockers with vasodilating effects have a better metabolic profile when compared with those that purely affect β receptors. Thus, vasodilating β blockers, by being neutral on glycemic and metabolic factors, are associated with less use of additional medication for lipid or glucose control and may provide a potentially greater cardiovascular risk reduction by virtue of these effects.
The Prevalence of Primary Aldosteronism in Diabetic Patients
Authors: Jefic Dijana , Mohiuddin Naushaba , Alsabbagh Rana , Fadanelli Margaret , Steigerwalt Susan
Published: February 2007

Increased plasma aldosterone concentrations (PACs) are associated with higher cardiovascular risk and target organ damage (TOD). Hyperglycemia can potentiate the cellular effects of aldosterone, and the prevalence of diabetes in primary aldosteronism (PA) is 7%–59%. The prevalence of PA in hypertensive individuals is estimated to be 10%–14%. This study of 61 hypertensive diabetic patients not taking spironolactone and with serum creatinine values <2.5 mg/dL sought to establish the prevalence of PA in hypertensive diabetics and compare the prevalence of PA in patients with TOD with those patients without TOD. PA was suspected if PACs were >15 ng/dL and plasma renin activity was <1 ng/dL/h (ratio >30). Although 14 patients had suppressed renin with PACs >8 ng/ dL (including two with PACs >11 ng/dL), none met our criteria for PA. There was no correlation between PAC and TOD. This study indicates that routine screening for PA in hypertensive diabetic patients is not justified and that PAC does not correlate with TOD. Further study is needed.
Long‐Term Effects of a Losartan‐Compared With an Atenolol‐Based Treatment Regimen on Carotid Artery Plaque Development in Hypertensive Patients With Left Ventricular Hypertrophy: ICARUS, a LIFE Substudy
Authors: Fossum Eigil , Olsen Michael Hecht , Høieggen Aud , Wachtell Kristian , Reims Henrik M. , Kjeldsen Sverre E. , Ibsen Hans , Wan Ying , Julius Stevo
Published: February 2007

In the Losartan Intervention for Endpoint Reduction in Hypertension (LIFE) study, there was a 25% risk reduction for stroke with angiotensin receptor blocker‐based therapy (losartan) as compared with β‐blocker‐based therapy (atenolol) despite comparable blood pressure reductions. This substudy examines treatment effects on the amount and density of atherosclerotic lesions in the common carotid arteries and the carotid bulb in 81 patients during 3 years of treatment. There were no statistically significant changes in the amount of carotid plaque in patients treated with losartan compared with an atenolol‐based treatment program. A statistically nonsignificant increase in plaque density and index (average of plaque amount and density) was seen in the atenolol group compared with those treated with losartan. The small number of patients evaluated may have limited the power to detect a difference in outcome. The difference in carotid plaque index increase between the treatment groups during 3 years of treatment could not be statistically linked to specific treatments in the present substudy.
Aldosterone—A Hormone of Cardiovascular Adaptation and Maladaptation
Authors: Goodfriend Theodore L.
Published: February 2007

Aldosterone stimulates reabsorption of sodium, sustaining blood volume and pressure in the face of salt deprivation or extracellular fluid depletion. The steroid also stimulates excretion of potassium, protecting extracellular fluid from excessive levels of that ion. These two actions are relatively rapid and clearly adaptive when appropriately initiated and terminated, but maladaptive when prolonged or excessive, causing hypertension and electrolyte imbalance. Aldosterone and other mineralocorticoids exert slower, direct effects on cells in the heart, kidneys, and vessels, leading to hypertrophy, fibrosis, and dysfunction contributing to degenerative cardiovascular diseases. The maladaptive actions of aldosterone are exacerbated by sodium chloride, angiotensin, endothelin, and certain growth factors. Damage can be minimized by antagonists of aldosterone receptors, inhibitors of the renin system, depletion of salt, and repletion of potassium and magnesium. Specific inhibitors of fibrosis and hypertrophy, and more effective inhibitors of the renin system should be useful in the future.
Antihypertensive Pharmacobezoar
Authors: Prisant L. Michael , Spaulding Vernon C.
Published: February 2007

Most antihypertensive drugs have known side effects that are elicited by the careful clinician taking care of hypertensive patients. However, many antihypertensive medications utilize drug delivery systems that prolong the duration of blood pressure reduction. The gastrointestinal therapeutic system that is used with nifedipine, isradipine, and verapamil has a unique side effect. Obstruction may occur at the site of a previous surgical repair (pyloric stenosis or gastroplasty) or stenosis of the esophagus, small intestine, or colon. The same delivery system is used with methylphenidate, oxy‐butynin, glipizide, and doxazosin. Although this complication is rare, physicians who prescribe and care for hypertensive patients should recognize this potential problem.
Niacin‐ER/Statin Combination for the Treatment of Dyslipidemia: Focus on Low High‐Density Lipoprotein Cholesterol
Authors: Chrysant Steven G. , Ibrahim Mohammad
Published: February 2007

Statins are effective drugs for lowering low‐density lipoprotein cholesterol, and their use has been associated with a significant decrease in cardiovascular morbidity and mortality. However, statins are ineffective in lowering plasma triglycerides and lipoprotein(a), or increasing low high‐density lipoprotein cholesterol (HDL‐C) plasma levels, which are independent risk factors for coronary heart disease. Niacin, on the other hand, is the most potent drug available for lowering plasma levels of triglycerides and lipoprotein(a) and raising HDL‐C levels. It follows, then, that a combination of niacin with a statin might be an effective combination in improving all components of the lipid profile. Previous studies have shown that the use of long‐acting niacin with a statin, in dose combinations of niacin‐ER/lovastatin 1000/20 mg or 2000/40 mg once daily, has been effective in favorably modifying low‐density lipoprotein cholesterol, triglycerides, lipoprotein(a), and HDL‐C plasma levels. Dyslipidemias often predate the onset of hypertension, and HDL‐C has been found to be inversely related to the incidence of hypertension. Normalization of lipid components, including the total cholesterol/HDL‐C ratio, is important in the management of hypertensive individuals and patients with the metabolic syndrome or diabetes. Thus, the long‐term treatment of dyslipidemias with these two agents may help to modify risk and reduce cardiovascular morbidity and mortality in these patients over and above benefits achieved by lowering blood pressure
Insulin Resistance, Diabetes, Hypertension, and Renin—Angiotensin System Inhibition: Reducing Risk for Cardiovascular Disease
Authors: Fonseca Vivian A.
Published: February 2007

Insulin resistance, diabetes mellitus, and hypertension are associated with significant cardiovascula: morbidity and mortality. Lifestyle modifications effectively decrease the risk of progression to diabetes in high‐risk patients, but intensive interventions can be costly and difficult for patients to maintain. The addition of pharmacotherapy is often necessary to treat hyperglycemia and hypertension and lower the risk of cardiovascular complications. Clinical trial data suggest the use of insulin‐sensitizing and antihyperglycemic agents to delay the progression to diabetes. Similarly, analysis of data from clinical trials of angiotensin‐converting enzyme inhibitors and angiotensin II receptor blockers indicate that the use of these agents results in fewer cases of new‐onset diabetes among patients with hypertension, when compared with other antihypertensive agents. Angiotensin II has direct and indirect effects on insulin and its signaling pathways, providing support for the biologic mechanism underlying the benefits of renin‐angiotensin system inhibition in preventing diabetes and cardiovascular events. Clinical trials now under way will further evaluate the role of renin‐angiotensin system inhibition in preventing diabetes and its microvascular and macrovascular complications.
Antihypertensive Prescribing Practices: Impact of the Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial
Authors: Player Marty S. , Gill James M. , Fagan Heather Bittner , Mainous Arch G.
Published: February 2007

This national study examines the impact of the Antihypertensive and Lipid‐Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) on the prescribing of thiazide‐type diuretics and other antihypertensive medications for patients with newly diagnosed hypertension. A cross‐sectional analysis was conducted using data from a national network of electronic health records for 2 groups with newly diagnosed hypertension and started on antihypertensive medications: one a year before and the other a year after the publication of ALLHAT. The percentage of new hypertensives started on thiazides increased from 29% pre‐ALLHAT to 39% post‐ALLHAT. An increase was also seen for angiotensin receptor blockers, while prescribing for angiotensin‐converting enzyme inhibitors, calcium channel blockers, and β‐blockers declined. There was no significant change in prescriptions for α‐blockers. Prescriptions for thiazides for patients with newly diagnosed hypertension increased after the publication of ALLHAT. Data from large national trials can have a considerable impact on prescribing practices.
Achieving Blood Pressure Goals: Why Aren't We?
Authors: Cushman William C. , Basile Jan
Published: February 2007

The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) recommends a blood pressure (BP) goal of <140/90 mm Hg in patients with hypertension and <130/80 mm Hg in those with diabetes or chronic kidney disease. Achievement of BP goals is associated with significant benefits in cardiovascular morbidity and mortality. Although evidence suggests these goals are attainable, only about one third of patients are meeting them. There is a significant gap between treatment guideline recommendations and their implementation in clinical practice. Many clinicians appear satisfied with modest BP reductions and do not make the necessary treatment adjustments to achieve BP goals. Patient nonadherence is another important reason for lack of BP control. For the success of clinical trials to be reproduced in clinical practice, clinicians must recognize the importance of treating BP to goal, emphasize to patients the need to adhere to treatments, and provide persistent, goal‐targeted therapy.
Angiotensin Receptor Blockade Improves Vascular Compliance in Healthy Normotensive Elderly Individuals: Results From a Randomized Double‐Blind Placebo‐Controlled Trial
Authors: Rajagopalan Sanjak , Kariisa Mbabazi , Dellegrottaglie Santo , Bard Robert L. , Kehrer Christine , Matlow Susan , Daley William , Pitt Bertram , Brook Robert
Published: February 2007

The renin‐angiotensin system (RAS) may play a role in vascular aging. The authors hypothesized that blockade of the angiotensin II type 1 receptor with an angiotensin receptor blocker in healthy elderly subjects improves vascular compliance and endothelial function. Thirty‐five healthy elderly subjects were randomized to valsartan or placebo in a double‐blind crossover study after baseline testing for pulse wave velocity, aortic augmentation index, and brachial artery flow‐mediated dilation. Angiotensin II type 1 receptor blockade with valsartan improved vascular compliance but not flowmediated dilation. Changes in pulse wave velocity with valsartan were correlated with change in central systolic blood pressure and pulse pressure and remained associated on multivariate analysis. Change in pulse wave velocity after adjusting for degree of blood pressure change, age, and sex remained correlated with assignment to the angiotensin receptor blocker but not placebo. These data suggest that angiotensin II type 1 receptor blockade improves aging‐related vascular compliance without alterations in flow‐mediated dilation. Mechanisms regulating compliance and endothelial function are complex and may not necessarily converge in aging.
Molecular basis of D variants in Chinese persons
Authors: Yan Lixing , Wu Junjie , Zhu Faming , Hong Xiaozhen , Xu Xianguo
Published: February 2007

BACKGROUND: Most studies of the molecular basis of D variants have been conducted in Caucasian and African populations. There are limited data on the molecular basis for D variants in Chinese populations.

STUDY DESIGN AND METHODS: With a blended monoclonal anti‐D and a sequential slide and tube typing protocol, red blood cells from greater than 99 percent of Han Chinese were tested for the D antigen. Samples that agglutinated weakly by tube method or that reacted only by indirect antiglobulin test (IAT) were classified as D variants. The D variant was tested by an RHD polymerase chain reaction with sequence specific primers and by gene sequencing to distinguish and characterize weak D and partial D alleles.

RESULTS: Of 305,572 samples from individual donations (305,475 [99.97%] were ethnic Han and 97 [0.032%] were ethnic minorities), 304,134 (99.53%) typed as D+. Five (0.0016%) typed as D variants (weak agglutination by tube). By IAT an additional 32 (0.0105%) typed as D variants and 1401 (0.46%) typed as D–. Weak D type 15 and RHD(K409K) alleles represented 72.7 percent of all weak D phenotypes. All partial D phenotypes were DVI Type 3 or DV. Three new weak D alleles carrying 594A>T and 602C>G (weak D Type 51), 92T>C (weak D type 52), and 740T>G (weak D type 53) mutations, respectively, were identified.

CONCLUSION: There are significant differences in the frequencies and molecular characteristics of D variants among indigenous Chinese populations, compared to Caucasian and African populations, which must be considered when developing clinical practices related to D variant blood donors, transfusion recipients, or obstetrical patients.
Long‐Term Results (Up to 16.5 Years) of Mitral Balloon Valvuloplasty in a Series of 518 Patients and Predictors of Long‐Term Outcome
Authors: FAWZY MOHAMED E. , FADEL BAHAA , AL‐SERGANI HANI , AL AMRI MOHAMMED , HASSAN WALID , ABDULBAKI KHALID , SHOUKRI MOHAMED , CANVER CHARLES
Published: February 2007

Objectives: To assess the long‐term results (up to 16.5 years) of mitral balloon valvuloplasty (MBV) and to identify predictors of restenosis and event‐free survival.

Methods and Results: We report the immediate and long‐term clinical and echocardiographic results in 518 patients, mean age 31 ± 11 years, who underwent successful MBV for severe mitral stenosis (MS) and were followed up for 0.5–16.5 (mean 6 ± 4.5) years. After MBV, mitral valve area (MVA) increased from 0.84 ± 0.2 to 1.83 ± 0.53 cm2 (P < 0.0001) as measured by catheter and from 0.92 ± 0.17 to 1.96 ± 0.29 cm2 (P < 0.0001) as measured by two‐dimensional echo. Restenosis occurred in 111 patients (21%) and it was less frequent in patients with low echo score (11%). Actuarial freedom from restenosis at 5, 10, 15 years was 85 ± 1%, 70 ± 3%, and 44 ± 5%, respectively, and was significantly higher in patients with low echo score. Event‐free survival (death, redo MBV, mitral valve replacement, New York Heart Association [NYHA] functional class III or IV) at 5, 10, 15 years was 89 ± 1%, 79 ± 2%, 43 ± 9%, respectively, and was significantly higher for patients with low echo score. Cox regression analysis identified mitral echocardiographic score (MES) > 8 (P < 0.0001), postprocedure mitral valve area (MVA) (P = 0.0015), and preprocedure functional class (P = 0.014) as predictors of restenosis and MES (P < 0.0001) and age (P < 0.0001) and postprocedure MVA (P = 0.015) as predictors of event‐free survival.

Conclusions: MBV provides excellent long‐term results for selected patients with MS. The long‐term outcome after this procedure can be predicted from baseline clinical and echocardiographic characteristics.