Phenotyping photosynthesis: yes we can

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Keller B, Soto J, Steier A, Portilla-Benavides AE, Raatz B, Studer B, Walter A, Muller O, Urban MO. 2024. Linking photosynthesis and yield reveals a strategy to improve light use efficiency in a climbing bean breeding population. Journal of Experimental Botany 75, 901–916.

Allometries of cell and tissue anatomy and photosynthetic rate across leaves of C3 and C4 grasses

Allometric relationships among the dimensions of leaves and their cells hold across diverse eudicotyledons, but have remained untested in the leaves of grasses. We hypothesised that geometric (proportional) allometries of cell sizes across tissues and of leaf dimensions would arise due to the coordination of cell development and that of cell functions such as water, nutrient and energy transport, and that cell sizes across tissues would be associated with light-saturated photosynthetic rate. We tested predictions across 27 globally distributed C3 and C4 grass species grown in a common garden. We found positive relationships among average cell sizes within and across tissues, and of cell sizes with leaf dimensions. Grass leaf anatomical allometries were similar to those of eudicots, with exceptions consistent with the fewer cell layers and narrower form of grass leaves, and the specialised roles of epidermis and bundle sheath in storage and leaf movement. Across species, mean cell sizes in each tissue were associated with light-saturated photosynthetic rate per leaf mass, supporting the functional coordination of cell sizes. These findings highlight the generality of evolutionary allometries within the grass lineage and their interlinkage with coordinated development and function.

Phenotypic variation in photosynthetic traits in wheat grown under field versus glasshouse conditions

Recognition of the untapped potential of photosynthesis to improve crop yields has spurred research to identify targets for breeding. The CO2-fixing enzyme Rubisco is characterized by a number of inefficiencies, and frequently limits carbon assimilation at the top of the canopy, representing a clear target for wheat improvement. Two bread wheat lines with similar genetic backgrounds and contrasting in vivo maximum carboxylation activity of Rubisco per unit leaf nitrogen (Vc,max,25/Narea) determined using high-throughput phenotyping methods were selected for detailed study from a panel of 80 spring wheat lines. Detailed phenotyping of photosynthetic traits in the two lines using glasshouse-grown plants showed no difference in Vc,max,25/Narea determined directly via in vivo and in vitro methods. Detailed phenotyping of glasshouse-grown plants of the 80 wheat lines also showed no correlation between photosynthetic traits measured via high-throughput phenotyping of field-grown plants. Our findings suggest that the complex interplay between traits determining crop productivity and the dynamic environments experienced by field-grown plants needs to be considered in designing strategies for effective wheat crop yield improvement when breeding for particular environments.

Into the Shadows and Back into Sunlight: Photosynthesis in Fluctuating Light

Photosynthesis is an important remaining opportunity for further improvement in the genetic yield potential of our major crops. Measurement, analysis, and improvement of leaf CO₂ assimilation (A) have focused largely on photosynthetic rates under light-saturated steady-state conditions. However, in modern crop canopies of several leaf layers, light is rarely constant, and the majority of leaves experience marked light fluctuations throughout the day. It takes several minutes for photosynthesis to regain efficiency in both sun-shade and shade-sun transitions, costing a calculated 10-40% of potential crop CO₂ assimilation. Transgenic manipulations to accelerate the adjustment in sun-shade transitions have already shown a substantial productivity increase in field trials. Here, we explore means to further accelerate these adjustments and minimize these losses through transgenic manipulation, gene editing, and exploitation of natural variation. Measurement andanalysis of photosynthesis in sun-shade and shade-sun transitions are explained. Factors limiting speeds of adjustment and how they could be modified to effect improved efficiency are reviewed, specifically nonphotochemical quenching (NPQ), Rubisco activation, and stomatal responses.

Faster than expected Rubisco deactivation in shade reduces cowpea photosynthetic potential in variable light conditions

Cowpea is the major source of vegetable protein for rural populations in sub-Saharan Africa and average yields are not keeping pace with population growth. Each day, crop leaves experience many shade events and the speed of photosynthetic adjustment to this dynamic environment strongly affects daily carbon gain. Rubisco activity is particularly important because it depends on the speed and extent of deactivation in shade and recovers slowly on return to sun. Here, direct biochemical measurements showed a much faster rate of Rubisco deactivation in cowpea than prior estimates inferred from dynamics of leaf gas exchange in other species^1-3. Shade-induced deactivation was driven by decarbamylation, and half-times for both deactivation in shade and activation in saturating light were shorter than estimates from gas exchange (≤53% and 79%, respectively). Incorporating these half-times into a model of diurnal canopy photosynthesis predicted a 21% diurnal loss of productivity and suggests slowing Rubisco deactivation during shade is an unexploited opportunity for improving crop productivity.

During photosynthetic induction, biochemical and stomatal limitations differ between Brassica crops

Interventions to increase crop radiation use efficiency rely on understanding of how biochemical and stomatal limitations affect photosynthesis. When leaves transition from shade to high light, slow increases in maximum Rubisco carboxylation rate and stomatal conductance limit net CO₂ assimilation for several minutes. However, as stomata open intercellular [CO₂ ] increases, so electron transport rate could also become limiting. Photosynthetic limitations were evaluated in three important Brassica crops: Brassica rapa, Brassica oleracea and Brassica napus. Measurements of induction after a period of shade showed that net CO₂ assimilation by B. rapa and B. napus saturated by 10 min. A new method of analyzing limitations to induction by varying intercellular [CO₂ ] showed this was due to co-limitation by Rubisco and electron transport. By contrast, in B. oleracea persistent Rubisco limitation meant that CO₂ assimilation was still recovering 15 min after induction. Correspondingly, B. oleracea had the lowest Rubisco total activity. The methodology developed, and its application here, shows a means to identify the basis of variation in photosynthetic efficiency in fluctuating light, which could be exploited in breeding and bioengineering to improve crop productivity.

Life history is a key factor explaining functional trait diversity among subtropical grasses, and its influence differs between C3 and C4 species

Life history and photosynthetic type both affect the economics of leaf physiological function. Annual plants have lower tissue densities and resource-use efficiencies than perennials, while C4 photosynthesis, facilitated in grasses by specific changes in leaf anatomy, improves photosynthetic efficiency and water-use efficiency, especially in hot climates. This study aimed to determine whether C4 photosynthesis affects differences in functional traits between annual and perennial species. We measured 26 traits and characterised niche descriptors for 42 grasses from subtropical China. Differences in the majority of traits were explained by life history. The ranges of annual species (particularly C4 annuals) extended to regions with greater temperature seasonality and lower precipitation, and annuals had less-negative turgor-loss points, higher specific leaf areas, and lower water-use efficiencies, stomatal conductances, and leaf areas per stem area than perennials. Photosynthetic type largely affected leaf physiology as expected, but interacted with life history in determining specific traits. Leaf hydraulic conductance was intermediate in perennials, highest in C4-annuals, and lowest in C3-annuals. Densities of stomata and stem vessels were similar across C3-perennials and C4 species, but stomatal densities were lower and stem vessel densities higher in C3-annuals. Phylogenetic principal component analysis confirmed that in this subtropical environment life history is the predominant axis separating species, and annuals and perennials were more different within C3 than C4 grasses. The interplay between life history and photosynthetic type may be an overlooked factor in shaping the physiological ecology of grasses.

Whole plant chamber to examine sensitivity of cereal gas exchange to changes in evaporative demand

BACKGROUND

Improving plant water use efficiency (WUE) is a major target for improving crop yield resilience to adverse climate change. Identifying genetic variation in WUE usually relies on instantaneous measurements of photosynthesis (An) and transpiration (Tr), or integrative measurements of carbon isotope discrimination, at the leaf level. However, leaf gas exchange measurements alone do not adequately represent whole plant responses, especially if evaporative demand around the plant changes.

RESULTS

Here we describe a whole plant gas exchange system that can rapidly alter evaporative demand when measuring An, Tr and intrinsic WUE (iWUE) and identify genetic variation in this response. An was not limited by VPD under steady-state conditions but some wheat cultivars restricted Tr under high evaporative demand, thereby improving iWUE. These changes may be ABA-dependent, since the barley ABA-deficient mutant (Az34) failed to restrict Tr under high evaporative demand. Despite higher Tr, Az34 showed lower An than wild-type (WT) barley because of limitations in Rubisco carboxylation activity. Tr and An of Az34 were more sensitive than WT barley to exogenous spraying with ABA, which restricted photosynthesis via substrate limitation and decreasing Rubisco activation.

CONCLUSIONS

Examining whole plant gas exchange responses to altered VPD can identify genetic variation in whole plant iWUE, and facilitate an understanding of the underlying mechanism(s).

CO2 availability influences hydraulic function of C3 and C4 grass leaves

Atmospheric CO2 (ca) has increased since the last glacial period, increasing photosynthetic water use efficiency and improving plant productivity. Evolution of C4 photosynthesis at low ca led to decreased stomatal conductance (gs), which provided an advantage over C3 plants that may be reduced by rising ca. Using controlled environments, we determined how increasing ca affects C4 water use relative to C3 plants. Leaf gas exchange and mass per area (LMA) were measured for four C3 and four C4 annual, crop-related grasses at glacial (200 µmol mol-1), ambient (400 µmol mol-1), and super-ambient (640 µmol mol-1) ca. C4 plants had lower gs, which resulted in a water use efficiency advantage at all ca and was broadly consistent with slower stomatal responses to shade, indicating less pressure on leaf water status. At glacial ca, net CO2 assimilation and LMA were lower for C3 than for C4 leaves, and C3 and C4 grasses decreased leaf hydraulic conductance (Kleaf) similarly, but only C4 leaves decreased osmotic potential at turgor loss. Greater carbon availability in C4 leaves at glacial ca generated a different hydraulic adjustment relative to C3 plants. At current and future ca, C4 grasses have advantages over C3 grasses due to lower gs, lower stomatal sensitivity, and higher absolute water use efficiency.

Slow induction of photosynthesis on shade to sun transitions in wheat may cost at least 21% of productivity

Wheat is the second most important direct source of food calories in the world. After considerable improvement during the Green Revolution, increase in genetic yield potential appears to have stalled. Improvement of photosynthetic efficiency now appears a major opportunity in addressing the sustainable yield increases needed to meet future food demand. Effort, however, has focused on increasing efficiency under steady-state conditions. In the field, the light environment at the level of individual leaves is constantly changing. The speed of adjustment of photosynthetic efficiency can have a profound effect on crop carbon gain and yield. Flag leaves of wheat are the major photosynthetic organs supplying the grain of wheat, and will be intermittently shaded throughout a typical day. Here, the speed of adjustment to a shade to sun transition in these leaves was analysed. On transfer to sun conditions, the leaf required about 15 min to regain maximum photosynthetic efficiency. In vivo analysis based on the responses of leaf CO₂ assimilation (A) to intercellular CO₂ concentration (c_i) implied that the major limitation throughout this induction was activation of the primary carboxylase of C3 photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This was followed in importance by stomata, which accounted for about 20% of the limitation. Except during the first few seconds, photosynthetic electron transport and regeneration of the CO₂ acceptor molecule, ribulose-1,5-bisphosphate (RubP), did not affect the speed of induction. The measured kinetics of Rubisco activation in the sun and de-activation in the shade were predicted from the measurements. These were combined with a canopy ray tracing model that predicted intermittent shading of flag leaves over the course of a June day. This indicated that the slow adjustment in shade to sun transitions could cost 21% of potential assimilation.

This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.

Promises and Challenges of Eco-Physiological Genomics in the Field: Tests of Drought Responses in Switchgrass

Identifying the physiological and genetic basis of stress tolerance in plants has proven to be critical to understanding adaptation in both agricultural and natural systems. However, many discoveries were initially made in the controlled conditions of greenhouses or laboratories, not in the field. To test the comparability of drought responses across field and greenhouse environments, we undertook three independent experiments using the switchgrass reference genotype Alamo AP13. We analyzed physiological and gene expression variation across four locations, two sampling times, and three years. Relatively similar physiological responses and expression coefficients of variation across experiments masked highly dissimilar gene expression responses to drought. Critically, a drought experiment utilizing small pots in the greenhouse elicited nearly identical physiological changes as an experiment conducted in the field, but an order of magnitude more differentially expressed genes. However, we were able to define a suite of several hundred genes that were differentially expressed across all experiments. This list was strongly enriched in photosynthesis, water status, and reactive oxygen species responsive genes. The strong across-experiment correlations between physiological plasticity-but not differential gene expression-highlight the complex and diverse genetic mechanisms that can produce phenotypically similar responses to various soil water deficits.

Maximal stomatal conductance to water and plasticity in stomatal traits differ between native and invasive introduced lineages of Phragmites australis in North America

The fitness costs of reproduction by clonal growth can include a limited ability to adapt to environmental and temporal heterogeneity. Paradoxically, some facultatively clonal species are not only able to survive, but colonize, thrive and expand in heterogeneous environments. This is likely due to the capacity for acclimation (sensu stricto) that compensates for the fitness costs and complements the ecological advantages of clonality. Introduced Phragmites australis demonstrates great phenotypic plasticity in response to temperature, nutrient availability, geographic gradient, water depths, habitat fertility, atmospheric CO2, interspecific competition and intraspecific competition for light. However, no in situ comparative subspecies studies have explored the difference in plasticity between the non-invasive native lineage and the highly invasive introduced lineage. Clonality of the native and introduced lineages makes it possible to control for genetic variation, making P. australis a unique system for the comparative study of plasticity. Using previously identified clonal genotypes, we investigated differences in their phenotypic plasticity through measurements of the lengths and densities of stomata on both the abaxial (lower) and adaxial (upper) surfaces of leaves, and synthesized these measurements to estimate impacts on maximum stomatal conductance to water (gwmax). Results demonstrated that at three marsh sites, invasive lineages have consistently greater gwmax than their native congeners, as a result of greater stomatal densities and smaller stomata. Our analysis also suggests that phenotypic plasticity, determined as within-genotype variation in gwmax, of the invasive lineage is similar to, or exceeds, that shown by the native lineage.

The genetics of divergence and reproductive isolation between ecotypes of Panicum hallii

The process of plant speciation often involves the evolution of divergent ecotypes in response to differences in soil water availability between habitats. While the same set of traits is frequently associated with xeric/mesic ecotype divergence, it is unknown whether those traits evolve independently or if they evolve in tandem as a result of genetic colocalization either by pleiotropy or genetic linkage. The self-fertilizing C4 grass species Panicum hallii includes two major ecotypes found in xeric (var. hallii) or mesic (var. filipes) habitats. We constructed the first linkage map for P. hallii by genotyping a reduced representation genomic library of an F2 population derived from an intercross of var. hallii and filipes. We then evaluated the genetic architecture of divergence between these ecotypes through quantitative trait locus (QTL) mapping. Overall, we mapped QTLs for nine morphological traits that are involved in the divergence between the ecotypes. QTLs for five key ecotype-differentiating traits all colocalized to the same region of linkage group five. Leaf physiological traits were less divergent between ecotypes, but we still mapped five physiological QTLs. We also discovered a two-locus Dobzhansky-Muller hybrid incompatibility. Our study suggests that ecotype-differentiating traits may evolve in tandem as a result of genetic colocalization.

Physiological advantages of C4 grasses in the field: a comparative experiment demonstrating the importance of drought

Global climate change is expected to shift regional rainfall patterns, influencing species distributions where they depend on water availability. Comparative studies have demonstrated that C4 grasses inhabit drier habitats than C3 relatives, but that both C3 and C4 photosynthesis are susceptible to drought. However, C4 plants may show advantages in hydraulic performance in dry environments. We investigated the effects of seasonal variation in water availability on leaf physiology, using a common garden experiment in the Eastern Cape of South Africa to compare 12 locally occurring grass species from C4 and C3 sister lineages. Photosynthesis was always higher in the C4 than C3 grasses across every month, but the difference was not statistically significant during the wettest months. Surprisingly, stomatal conductance was typically lower in the C3 than C4 grasses, with the peak monthly average for C3 species being similar to that of C4 leaves. In water-limited, rain-fed plots, the photosynthesis of C4 leaves was between 2.0 and 7.4 μmol m(-2) s(-1) higher, stomatal conductance almost double, and transpiration 60% higher than for C3 plants. Although C4 average instantaneous water-use efficiencies were higher (2.4-8.1 mmol mol(-1)) than C3 averages (0.7-6.8 mmol mol(-1)), differences were not as great as we expected and were statistically significant only as drought became established. Photosynthesis declined earlier during drought among C3 than C4 species, coincident with decreases in stomatal conductance and transpiration. Eventual decreases in photosynthesis among C4 plants were linked with declining midday leaf water potentials. However, during the same phase of drought, C3 species showed significant decreases in hydrodynamic gradients that suggested hydraulic failure. Thus, our results indicate that stomatal and hydraulic behaviour during drought enhances the differences in photosynthesis between C4 and C3 species. We suggest that these drought responses are important for understanding the advantages of C4 photosynthesis under field conditions.

Genotypic variation in traits linked to climate and aboveground productivity in a widespread C₄ grass: evidence for a functional trait syndrome

Examining intraspecific variation in growth and function in relation to climate may provide insight into physiological evolution and adaptation, and is important for predicting species responses to climate change. Under common garden conditions, we grew nine genotypes of the C₄ species Panicum virgatum originating from different temperature and precipitation environments. We hypothesized that genotype productivity, morphology and physiological traits would be correlated with climate of origin, and a suite of adaptive traits would show high broad-sense heritability (H(2)). Genotype productivity and flowering time increased and decreased, respectively, with home-climate temperature, and home-climate temperature was correlated with genotypic differences in a syndrome of morphological and physiological traits. Genotype leaf and tiller size, leaf lamina thickness, leaf mass per area (LMA) and C : N ratios increased with home-climate temperature, whereas leaf nitrogen per unit mass (Nm ) and chlorophyll (Chl) decreased with home-climate temperature. Trait variation was largely explained by genotypic differences (H(2) = 0.33-0.85). Our results provide new insight into the role of climate in driving functional trait coordination, local adaptation and genetic divergence within species. These results emphasize the importance of considering intraspecific variation in future climate change scenarios.

Plant growth rates and seed size: a re-evaluation

Small-seeded plant species are often reported to have high relative growth rate or RGR. However, because RGR declines as plants grow larger, small-seeded species could achieve higher RGR simply by virtue of their small size. In contrast, size-standardized growth rate or SGR factors out these size effects. Differences in SGR can thus only be due to differences in morphology, allocation, or physiology. We used nonlinear regression to calculate SGR for comparison with RGR for 10 groups of species spanning a wide range of life forms. We found that RGR was negatively correlated with seed mass in nearly all groups, but the relationship between SGR and seed mass was highly variable. We conclude that small-seeded species only sometimes possess additional adaptations for rapid growth over and above their general size advantage.

Photosynthetic pathway and ecological adaptation explain stomatal trait diversity amongst grasses

• The evolution of C(4) photosynthesis in plants has allowed the maintenance of high CO(2) assimilation rates despite lower stomatal conductances. This underpins the greater water-use efficiency in C(4) species and their tendency to occupy drier, more seasonal environments than their C(3) relatives. • The basis of interspecific variation in maximum stomatal conductance to water (g(max) ), as defined by stomatal density and size, was investigated in a common-environment screening experiment. Stomatal traits were measured in 28 species from seven grass lineages, and comparative methods were used to test for predicted effects of C(3) and C(4) photosynthesis, annual precipitation and habitat wetness on g(max) . • Novel results were as follows: significant phylogenetic patterns exist in g(max) and its determinants, stomatal size and stomatal density; C(4) species consistently have lower g(max) than their C(3) relatives, associated with a shift towards smaller stomata at a given density. A direct relationship between g(max) and precipitation was not supported. However, we confirmed associations between C(4) photosynthesis and lower precipitation, and showed steeper stomatal size-density relationships and higher g(max) in wetter habitats. • The observed relationships between stomatal patterning, photosynthetic pathway and habitat provide a clear example of the interplay between anatomical traits, physiological innovation and ecological adaptation in plants.

Drought limitation of photosynthesis differs between C₃and C₄grass species in a comparative experiment

Phylogenetic analyses show that C₄ grasses typically occupy drier habitats than their C₃ relatives, but recent experiments comparing the physiology of closely related C₃ and C₄ species have shown that advantages of C₄ photosynthesis can be lost under drought. We tested the generality of these paradoxical findings in grass species representing the known evolutionary diversity of C₄ NADP-me and C₃ photosynthetic types. Our experiment investigated the effects of drought on leaf photosynthesis, water potential, nitrogen, chlorophyll content and mortality. C₄ grasses in control treatments were characterized by higher CO₂ assimilation rates and water potential, but lower stomatal conductance and nitrogen content. Under drought, stomatal conductance declined more dramatically in C₃ than C₄ species, and photosynthetic water-use and nitrogen-use efficiency advantages held by C₄ species under control conditions were each diminished by 40%. Leaf mortality was slightly higher in C₄ than C₃ grasses, but leaf condition under drought otherwise showed no dependence on photosynthetic-type. This phylogenetically controlled experiment suggested that a drought-induced reduction in the photosynthetic performance advantages of C₄ NADP-me relative to C₃ grasses is a general phenomenon.

Partitioning the components of relative growth rate: how important is plant size variation?

Plant growth plays a key role in the functioning of the terrestrial biosphere, and there have been substantial efforts to understand why growth varies among species. To this end, a large number of experimental analyses have been undertaken; however, the emergent patterns between growth rate and its components are often contradictory. We believe that these conflicting results are a consequence of the way growth is measured. Growth is typically characterized by relative growth rate (RGR); however, RGR often declines as organisms get larger, making it difficult to compare species of different sizes. To overcome this problem, we advocate using nonlinear mixed-effects models so that RGR can be calculated at a standard size, and we present easily implemented methods for doing this. We then present new methods for analyzing the traditional components of RGR that explicitly allow for the fact that (log)(RGR) is the sum of its components. These methods provide an exact decomposition of the variance in (log)(RGR). Finally, we use simple analytical and simulation approaches to explore the effect of size variation on growth and its components and show that the relative importance of the components of RGR is influenced by the extent to which analyses standardize for plant size.

Ecophysiological traits in C3 and C4 grasses: a phylogenetically controlled screening experiment

Experimental evidence demonstrates a higher efficiency of water and nitrogen use in C(4) compared with C(3) plants, which is hypothesized to drive differences in biomass allocation between C(3) and C(4) species. However, recent work shows that contrasts between C(3) and C(4) grasses may be misinterpreted without phylogenetic control. Here, we compared leaf physiology and growth in multiple lineages of C(3) and C(4) grasses sampled from a monophyletic clade, and asked the following question: which ecophysiological traits differ consistently between photosynthetic types, and which vary among lineages? C(4) species had lower stomatal conductance and water potential deficits, and higher water-use efficiency than C(3) species. Photosynthesis and nitrogen-use efficiency were also greater in C(4) species, varying markedly between clades. Contrary to previous studies, leaf nitrogen concentration was similar in C(4) and C(3) types. Canopy mass and area were greater, and root mass smaller, in the tribe Paniceae than in most other lineages. The size of this phylogenetic effect on biomass partitioning was greater in the C(4) NADP-me species than in species of other types. Our results show that the phylogenetic diversity underlying C(4) photosynthesis is critical to understanding its functional consequences. Phylogenetic bias is therefore a crucial factor to be considered when comparing the ecophysiology of C(3) and C(4) species.

A double-blind, placebo-controlled, parallel dose-response study of amlodipine in stable exertional angina pectoris

A placebo-controlled, double-blind, dose-response study of amlodipine (1.25, 2.5, 5, and 10 mg once daily) was carried out in 136 patients with stable exertional angina pectoris. Improvements in total exercise tolerance, time to onset of angina during exercise, ST-segment deviation at maximum common load, frequency of angina attacks, and nitroglycerin consumption were greater following amlodipine than placebo. The maximum improvement in exercise parameters occurred with the highest dose of amlodipine. All doses produced significant reductions in angina attack frequency and the rate of nitroglycerin consumption. Amlodipine was well tolerated and no patients were withdrawn due to adverse events or laboratory abnormalities.

Social work practice with people with disabilities in the era of disability rights

Social workers, especially those in health care and rehabilitation systems, must consider practice changes necessitated by recent legislation and the growing activism of disability rights groups. The authors review essential elements of the emerging sense of both oppression and empowerment that is occurring for many people with disabilities and groups; consider key aspects of ADA and other perti nent legislation that place new emphases on the self-determination of people with disabilities; and discuss what implications changing practice roles might have for social workers' relationships and patterns of interaction with other professionals in medical, health care and rehabilitation settings. The authors outline a beginning effort at designing a conceptual framework that promotes practice that: (1) maximizes clients' involvement in exploring an expanded range of options and choices; (2) prepares clients to be more effective in dealings with professionals, bureaucrats and agencies that often do not understand nor appreciate their need for self-determination; and (3) at the organizing level, mobilizes and helps to empower groups of people with disabilities to consider policy and program alternatives that can improve their situation. This framework may also be useful in work with people who have other long term care needs, chronic conditions.

Diuretic therapy in congestive heart failure

The principal goals of treatment of the patient in heart failure are the relief of their symptoms and improvement in their prognosis. Of all antiheart failure drugs currently available, the diuretics are therapeutically superior in their efficacy in relieving clinical symptoms and signs. Whether administered intravenously or orally, all diuretics result in a substantial reduction in the raised pulmonary vascular pressures in combination with a small reduction in cardiac output. Diuretics stimulate release of renin with subsequent activation of the renin-angiotensin-aldosterone system, particularly if used in large doses, although their quantitative impact on the neuroendocrine profile at different stages of heart failure remains to be defined. In patients with mild heart failure, diuretics reduce plasma catecholamine concentrations, but their sympatholytic effects in more severe cases are unknown, as are their effects on the metabolically active tissues in these patients. Diuretic resistance can be circumvented by segmental nephron blockade with a combination of low-dose diuretics that simultaneously block sodium reabsorption in the proximal tubule, the loop of Henle, the distal tubule, and the collecting duct. Diuretics improve symptoms of breathlessness and signs of peripheral edema in patients with congestive heart failure in direct relationship to the induced diuresis. These benefits are frequently associated with a substantial improvement in patients' appreciation of quality of life and economic capacity. There are few adverse reactions to chronic diuretic therapy, but the serum electrolytes should be monitored for hypokalemia and hypomagnesemia. The impact of diuretics on prognosis of patients with congestive heart failure is unknown; however, diuretics have been a major ingredient of the therapies used in all the survival trials with vasodilators, angiotensin-converting enzyme inhibitors, and beta-blocking drugs. In addition to their clinical benefits, diuretics are the most cost-effective treatment of any single drug group currently available for the treatment of patients with congestive heart failure.

Diuretics in cardiovascular therapy: the new clinicopharmacological bases that matter

Diuretics in current use include early distal tubular (i.e., thiazide-type), loop (i.e., furosemide-type), and potassium-and-hydrogen-retaining substances. Available oral formulations of diuretics differ in terms of their renal excretory potency in man, as formally assessed through the effect of a single dose on 24-hour natriuresis in healthy subjects. The 2.5 mg formulation of the loop diuretic torasemide does not increase mean 24-hour natriuresis, and it is therefore considered a very-low-dose formulation. Amiloride 5 mg and torasemide 5 mg and 10 mg, which increase mean 24-hour natriuresis by less than 40%, are considered low-dose or low-potency diuretic formulations of diuretic substances. Hydrochlorothiazide 25 and 50 mg, furosemide 40 and 80 mg, and torasemide 20 mg, which increase mean 24-hour natriuresis by more than 40%, are considered high-dose or high-potency formulations. A rebound in natriuresis follows the early-after-dosing increase in this variables caused by loop diuretics; hence many oral formulations of loop substances are less potent natriuretics than most oral formulations of thiazide-type diuretics. Hydrochlorothiazide 25 mg and furosemide 80 mg have similar natriuretic potencies. During once-daily administration of diuretic formulations of diuretics to subjects without edema and normal renal function, the increases in 24-hour natriuresis and diuresis that follow the first dose disappear or attenuate markedly. This is due to neuroendocrine reactions to diuretic-induced sodium loss and its attendant hemodynamic shifts. Some of these reactions, e.g. the increase in plasma aldosterone that takes place, account for an elevation in kaliuresis that occurs during once-daily treatment with a high-dose formulation of a thiazide-type diuretic. Common fixed-dose combinations of a thiazide-type or a loop diuretic and a potassium-and-hydrogen-retaining substance generally do not change kaliuresis, but they increase natriuresis strikingly. Thiazide-type and loop diuretics decrease and increase calciuresis respectively; none of these actions wanes during prolonged administration. Plasma renin activity and aldosterone do not rise in response to very-low-dose formulations of loop diuretics taken once daily. Glomerular filtration rate tends to fall in the course of once-daily administration of high-dose formulations of diuretics, but not during prolonged once-daily treatment with very-low-dose formulations of loop diuretics.

Hemodynamic differences between metoprolol and carvedilol in hypertensive patients

Resting hemodynamics were measured before, at 2 and 24 h after the first dose, and after 4 weeks of monotherapy with either metoprolol or carvedilol in a randomized single-blind study. We analyzed results from 24 hypertensive patients (30-68 years of age) with adequate blood-pressure lowering on monotherapy. Acutely, both drugs lowered systolic blood pressure and heart rate. Whereas metoprolol reduced cardiac output and increased both systemic and femoral artery resistance, carvedilol did not alter cardiac output but led to reductions in the systemic and regional resistances. After 4 weeks of therapy, cardiac output remained reduced and vascular resistances increased in the metoprolol group, whereas in carvedilol patients cardiac output continued to be unchanged and the trend for vascular resistances to be decreased persisted. Acutely and chronically the differences in the hemodynamic effects of the two medications were statistically significant. The study results indicate that carvedilol's vasodilatory action is not subject to tolerance development. Chronic afterload reduction associated with the decrease in systemic vascular resistance may lead to additional savings in myocardial oxygen consumption, a beneficial feature particularly in those patients with concomitant ischemic heart disease. It may also have a favorable influence on concentric cardiac hypertrophy and changes in the walls of arteriolar resistance vessels.

Comparison of the hemodynamic effects of metoprolol and carvedilol in hypertensive patients

Metoprolol and carvedilol are widely used in the treatment of hypertension, but no randomized comparison of their hemodynamic activity has been previously reported. Their comparative effects on heart rate, systemic blood pressure, and echocardiographically determined aortic and femoral artery blood flow were measured at rest and at 2 and 24 hours after the first dose of each drug, and again after 4 weeks of sustained monotherapy in 12 male and 12 female patients, aged 36-68 years with uncomplicated sustained hypertension according to a randomized single-blind protocol. Nine patients in each drug group achieved the target diastolic blood pressure of < 90 mmHg on the initial doses of each drug; this was achieved in the remainder following doubling of each dose. Neither drug occasioned withdrawal of any patient due to adverse reactions. Both drugs significantly reduced heart rate, although the reduction at 2 hours was significantly greater after metoprolol than after carvedilol. Both drugs reduced systolic pressure throughout the study; the reduction at 2 hours was significantly greater after carvedilol than after metoprolol. In contrast, the diastolic blood pressure was persistently reduced only by carvedilol. The cardiac output, determined as the aortic systolic blood flow, after carvedilol was not significantly different from pretreatment values throughout the study but was significantly reduced in the metoprolol-treated patients at each point of measurement. After metoprolol the systemic and femoral vascular resistances derived from conventional formulae were consistently and significantly increased over pretreatment values throughout the study and were significantly greater than in the carvedilol group at all measurement points. The hemodynamic differences between these two beta-blocking drugs may be explained by the additional vasodilator activity of carvedilol associated with its alpha 1-adrenoceptor blocking activity. The long-term clinical and prognostic implications of these pharmacodynamic differences between beta-adrenoceptor antagonists with and without additional vasodilator activity in the treatment of hypertensive patients remain to be determined.

Congestive heart failure. Towards a comprehensive treatment

Heart failure constitutes an increasing health hazard with major demands on health care resources. Recent major advances in drug treatment have yet to be translated into increased survival of heart failure patients in the community at large. Failure of diagnosis is a major factor in delaying early and adequate treatment. Echocardiography probably provides the most reliable and inexpensive instrument to confirm the diagnosis and pinpoint the mechanical components of the syndrome. The targets for therapeutic intervention may be categorized (i) haemodynamic, neuroendocrine and metabolic disorders (ii) symptoms and quality of life, (iii) morbidity and mortality risks. Symptoms and quality of life are the prime concerns of the physician in the treatment in the individual patient. Selection of anti-heart failure drugs used should be based on knowledge of the impact on the pathophysiological disorders and on the morbidity and mortality risks. Diuretics, vasodilators and ACE-inhibitors are now accepted as standard treatment, particularly when used in combination. Controversy continues to surround the efficacy of digitalis glycosides; they improve symptoms in some patients but their impact on morbidity and mortality risks is still uncertain. Even with standard treatments, may practical therapeutic questions remain, one of which is what is the most efficacious dose of each anti-heart failure drug which, when used in combination, will give the maximum improvement in quality of life and greatest extension of survival? Despite available treatment with diuretics, digitalis, vasodilators and ACE-inhibitors, the morbidity and mortality risks of congestive heart failure remain high. None of these drug groups significantly modulates the excessive excitation of the sympathoadrenal system, one of the two major neuroendocrine hazards of heart failure. For this reason, amongst the many newer drugs in development, the beta-adrenoceptor antagonists hold considerable promise as the next step towards a more comprehensive treatment of congestive heart failure.

Reoperation for recurrent metastatic brain tumors

Results of reoperation in 48 patients who developed recurrent brain metastases between January 1984 and April 1993 are presented. Median time from first craniotomy to diagnosis of recurrence (time to recurrence) was 6.7 months. Median Karnofsky performance scale (KPS) score prior to reoperation was 80. Recurrence was local in 30 patients, distant in 16 patients, and both local and distant in two patients. Median survival time after reoperation was 11.5 months. There were no operative mortalities. Multivariate analysis revealed that presence of systemic disease (p = 0.008), KPS scores less than or equal to 70 (p = 0.008), time to recurrence of less than 4 months (p = 0.008), age greater than or equal to 40 years (p = 0.51), and primary tumor type of breast or melanoma (p = 0.028) negatively affected patient survival time. These five factors were used to develop a grading system (Grades I-IV). Patients categorized in Grade I had a 5-year survival rate of 57%, whereas the median survival time of patients in Grades II, III, and IV was 13.4, 6.8, and 3.4 months, respectively (p < 0.0001). Overall, 26 patients developed a second recurrence after reoperation. Seventeen patients underwent a second reoperation, whereas nine did not. Patients undergoing a second reoperation survived a median of 8.6 additional months versus 2.8 months for those who did not (p < 0.0001). This study concludes that reoperation for recurrent brain metastasis can prolong survival and improve quality of life. A second reoperation can also increase survival. Five factors influence survival: status of systemic disease, KPS score, time to recurrence, age, and type of primary tumor. The grading system using these five factors correlates with survival time. Reoperation should be approached with caution in Grade IV patients because of their poor prognosis.

Refocus on diuretics in the treatment of heart failure

Diuretics have long been accepted as the traditional first-line treatment of the patient with symptomatic heart failure whatever its aetiology or dysfunctional stage. Their acceptance in this role is based on the rapid improvement in congestive symptoms experienced by most patients, which is arguably greater than that induced by any other currently available anti-heart failure drug. This symptomatic efficacy and their universal clinical acceptance as first-step treatment for the patient with symptoms of heart failure has precluded formal examination of their impact on prognosis. Evidence from indirect studies suggests that when used alone they may not be able to prevent clinical deterioration, possibly due to excitation of the renin-angiotensin-aldosterone system. When such excitation is suppressed by concomitant administration of angiotensin-converting enzyme inhibitors, relief of congestive symptoms is enhanced and the morbidity and mortality risk of heart failure significantly reduced. Studies on the mechanisms of diuretic resistance have demonstrated the synergy of diuretic activity when low doses of diuretics acting at different sites of the nephron are used in combination. Diuretics remain the cornerstone of treatment for symptoms in congestive heart failure but their overall efficacy is substantially improved when combined with ACE inhibitors.

Sarcoma metastatic to the brain: results of surgical treatment

We report on 21 patients surgically treated for intraparenchymal brain metastasis from sarcoma, including six osteosarcomas, four leiomyosarcomas, three malignant fibrous histiocytomas, two alveolar soft-part sarcomas, two Ewing's bone sarcomas, one extraskeletal osteosarcoma, one extraskeletal Ewing's sarcoma, and two unclassified sarcomas. Median survival after craniotomy was 11.8 months. Patients with a preoperative Karnofsky performance score of > 70 survived for 15.7 versus 6.6 months for those with a Karnofsky performance score < or = 70. Patients. undergoing complete resection survived 14.0 versus 6.2 months for patients undergoing incomplete resection. Patients with evidence of lung metastases at the time of surgery survived 11.8 months, which was similar to the 10.5-month survival for patients with disease limited to the brain. The two patients with alveolar soft-part sarcoma are alive at 16 and 25 months after surgery. We conclude that surgery is effective in treating selected patients with sarcoma metastatic to the brain and that patients with metastasis from alveolar soft-part sarcoma may have a relatively good prognosis if they are surgically treated. The complete removal of all brain metastases and a Karnofsky performance score > 70 are associated with a favorable prognosis, whereas the presence of concurrent lung metastases is not a contraindication to surgery.

Effect of pregnancy on prognosis for young women with breast cancer

Breast cancer in women under 30 years old carries a poor prognosis, for reasons that have not been identified. This study aimed to identify prognostic factors in this age group. Special attention was paid to the history of pregnancy. The clinical presentation and course of breast cancer was documented for 407 women, aged 20-29 years, who registered between 1978 and 1988 at one of nine cancer centres. Eligible patients had histologically confirmed local or regional invasive breast carcinoma, and received part or all of their initial therapy at the participating hospital. For patients whose breast cancers were diagnosed during pregnancy, the risk of dying from breast cancer was significantly greater than that of women who had never been pregnant (relative risk 3.26 [95% CI 1.81-5.87], p = 0.0004). Adjustment for number of axillary nodes affected and tumour diameter reduced the relative risk only slightly (2.83 [1.24-6.45], p = 0.023). For each 1-year increment in the time between the latest previous pregnancy and breast cancer diagnosis, the risk of dying decreased by 15% (relative risk 0.85, p = 0.011). Thus concurrent or recent previous pregnancy adversely affects survival of breast cancer in young women. The size of the effect is such that it probably contributes substantially to the poor prognosis of breast cancer in this age group as a whole.

Occurrence and prognosis of contralateral carcinoma of the breast

Of the 4,554 patients who registered at The University of Texas M. D. Anderson Cancer Center, Houston, Texas from 1965 to 1988 with a diagnosis of carcinoma of the breast and who underwent surgical treatment of at least one carcinoma of the breast at this institution, 142 had either a history of a prior carcinoma of the breast (metachronous; n = 55) or a contralateral carcinoma of the breast detected within four months of registration (synchronous; n = 87). We retrospectively studied the records of these 142 patients and found that the occurrence of bilateral carcinoma of the breast was low (3.1 percent), the frequency of metachronous carcinoma of the breast remained relatively constant over time, the nodal status of the second carcinoma of the breast correlated with the method of discovery rather than the stage of the first carcinoma of the breast and survival rates from the second carcinoma of the breast were similar for metachronous and synchronous disease. These data support the role of vigilant surveillance of the contralateral breast with screening at the time of initial diagnosis and during follow-up evaluation. Because the likelihood of detecting a second carcinoma of the breast at an early stage is high, with subsequent good survival rates, the use of prophylactic mastectomy should be very selective and based on the emotional needs of the patient.

Usefulness of amlodipine for angina pectoris

Calcium antagonists are effective antianginal agents in the treatment of patients with stable exercise-induced angina pectoris. A series of randomized, double-blind, placebo-controlled studies with the novel, once-daily calcium antagonist amlodipine have been completed in a large number of patients with stable exercise-induced angina pectoris. Compared with placebo, once-daily amlodipine demonstrated a significant dose-related extension in exercise duration and workload accomplished, and reduction in number of anginal attacks and associated glyceryl trinitrate consumption. The clinical antianginal attributes of amlodipine were accompanied by significant reductions in electrocardiographic evidence of myocardial ischemia. In comparison with other antianginal drugs, once-daily amlodipine at a dosage range of 5-10 mg demonstrated antianginal activity comparable to thrice-daily diltiazem and once-daily nadolol. Amlodipine administered once daily achieves symptomatic and electrocardiographic amelioration of myocardial ischemic episodes induced by exercise in the majority of patients with stable angina pectoris. Amlodipine does not depress left ventricular pumping activity, and its side-effect profile does not differ substantially from that of placebo.

Double-blind comparison of amlodipine and nifedipine retard in the treatment of mild to moderate hypertension

The efficacy and safety profiles of amlodipine (5-10 mg once daily) and nifedipine retard (20-40 mg twice daily) were compared in 111 hypertensive patients (sitting DBP in 95-115 mmHg) during eight weeks of treatment in a randomised double-blind parallel group study. BP was measured 22-24 hours after the daily dose of amlodipine and 10-12 hours after a dose of nifedipine retard. Baseline sitting BPs of 175/105 mmHg and 168/104 mmHg were significantly reduced (P < 0.05) to 157/93 mmHg and 151/92 mmHg at the end of treatment in response to mean daily doses of amlodipine 7.3 mg and nifedipine retard 58.9 mg. There were no clinically significant changes in heart rate with either treatment. Three patients in the amlodipine group and five patients in the nifedipine retard group could not be considered in analysis. The total numbers of adverse events (considered related or possibly related to treatment) (42 vs. 36) as well as the numbers of patients experiencing such events (22 vs. 22) were similar in the amlodipine and nifedipine retard treated groups, respectively, but with a greater incidence of headaches in response to nifedipine retard and of oedema in response to amlodipine. Five patients in each treatment group discontinued therapy due to such events. Overall the results showed once daily amlodipine as equivalent to twice daily nifedipine retard in the management of mild to moderate hypertension.

Captopril versus digoxin in patients with coronary artery disease and mild heart failure. A prospective, double-blind, placebo-controlled multicenter study. The CADS Study Group

We conducted a prospective, double-blind, placebo-controlled multicenter trial in order to evaluate the long-term effects of captopril (50 mg/day), digoxin (0.25 mg/day) and placebo on quality of life, cardiovascular events, clinical symptoms and exercise tolerance in patients with documented myocardial infarction, resulting in regional wall motion abnormalities, and with mild heart failure (NYHA class II to III without treatment) and exercise not limited by angina. 222 patients were studied, 63 were randomized to captopril, 66 to digoxin, 67 to placebo. Follow-up was conducted for two years. Base line characteristics in the three treatment groups were similar. After one year of therapy, digoxin had significantly improved general well-being (p < 0.01 vs captopril), symptom score (p < 0.05 vs captopril and placebo), and vitality (p < 0.05 vs captopril). Digoxin improved NYHA class in 45% as compared to placebo (28%, p < 0.05). Worsening of angina was more frequent with captopril as compared to digoxin (p < 0.05). However, cardiovascular events during follow-up were lower in the captopril group as compared to placebo and digoxin (p < 0.01 captopril vs placebo). No differences between groups were observed in baseline and follow-up exercise tolerance between the three groups. Dizziness during upright tilt and cough were more frequent with captopril as compared to digoxin or placebo. After two years of follow-up (captopril n = 32, digoxin n = 29, placebo n = 27) general well-being was improved with both digoxin and captopril (p < 0.004 and p < 0.03 vs placebo).(ABSTRACT TRUNCATED AT 250 WORDS)

Diuretics in postinfarction heart failure

Severe left ventricular failure, as evidenced by radiographic pulmonary edema or raised left ventricular filling pressure, accompanying acute myocardial infarction, carries a high mortality risk. In this situation, the intravenous loop-diuretic furosemide induces a rapid reduction in the raised left ventricular filling pressure due to an immediate and substantial increase in systemic venous compliance accompanied by increasing diuresis. This diuretic-induced venodilatation is probably due to the release of prostaglandins. The transient systemic arterial constriction and small increase in systemic blood pressure that follows intravenous furosemide probably results from the release of renin and subsequent activation of angiotensin. These diuretic induced hemodynamic changes are accompanied by restoration of the vasodilator reflex, which enables the heart to accommodate an acute volume load. Orally administered loop diuretics achieve slower, but similar, directional hemodynamic changes. There is no information on hemodynamic or neuroendocrine dose-response effects of loop diuretics, and there is no information pertaining to the use of other diuretic groups in this situation. The hemodynamic changes induced by furosemide summate with the changes induced by other anti-heart-failure drugs. In this subset of patients with acute myocardial infarction and severe heart failure, the influence of the diuretics on morbidity incidence and mortality risk remains to be measured.

Impact of adjuvant mitotane on the clinical course of patients with adrenocortical cancer

BACKGROUND

Adrenocortical carcinoma is a rare and aggressive disease with a poor prognosis. Adjuvant mitotane administration has been suggested as a strategy that might improve the outcome of patients with localized disease.

METHODS

The authors analyzed the clinical outcome of patients with localized or regional adrenocortical cancer. The study included 19 patients who were registered at M.D. Anderson Cancer Center during a 3-year period and who had localized or regional disease at the time of surgery. Of these, eight patients received mitotane postoperatively and continued the drug until their last contact or recurrence (Group A, adjuvant); five patients began taking mitotane after surgery but discontinued it after 2-12 months for reasons unrelated to the disease (Group P, postoperative); and six patients did not receive mitotane (Group N, no mitotane). All patients have been followed for at least 12 months.

RESULTS

The treatment groups differed significantly in their time to recurrence; the disease-free interval was shortest in Group A (P = 0.0055, by log-rank test). There was no statistical difference in survival among the groups, but the profile remained unfavorable for Group A. The 2-year survival rate was 100% for Groups N and P but only 43% for Group A. Of the potentially confounding factors, gender, age, steroid hypersecretion, and tumor size, none had any influence on recurrence or survival rates.

CONCLUSIONS

These findings do not support the conclusion that adjuvant mitotane is beneficial in patients with localized or regional adrenocortical cancer. Neither the disease-free interval nor survival was improved by the drug. The authors suggest that alternative therapeutic strategies be explored for the management of these patients.

Incidence of hypercalcemia in patients with malignancy referred to a comprehensive cancer center

BACKGROUND

Hypercalcemia is a serious and not infrequent complication of malignant diseases; precise information about the incidence of hypercalcemia is not readily available. The study was designed to determine the incidence of hypercalcemia in patients with cancer.

METHODS

Retrospective analysis was done of laboratory data from 7667 patients registered at M.D. Anderson Cancer Center for the first time during 1989 for whom serum calcium levels were determined during the first 2 months after registration.

RESULTS

Severe hypercalcemia (serum calcium level of more than 12.0 mg/100 ml) was present in 40 patients (0.52%); it occurred most often in patients with renal cell cancer (1.42%) and non-small cell lung cancer (1.03%). Less frequent diagnoses were multiple myeloma (0.79%), leukemia (0.63%), non-Hodgkin lymphoma (0.26%), and cancer of the gastrointestinal tract (0.20%). Moderate hypercalcemia (calcium levels of 10.8-12.0 mg/100 ml) was present in 48 patients (0.63%); it occurred most often in patients with renal cell cancer (3.30%) and multiple myeloma (2.38%). Less frequent diagnoses were non-small cell lung cancer (0.89%), non-Hodgkin lymphoma (0.79%), leukemia (0.63%), and cancer of the gastrointestinal tract (0.51%). The presence of hypercalcemia was associated with increased frequency of distant metastases, bone metastases, and increased mortality consistent with other studies of the prognostic effect of this complication.

CONCLUSIONS

Hypercalcemia may appear as a frequent complication in patients with cancer at some time during the course of their disease, but its incidence is relatively low.

Incidence of hypercalcemia in patients with malignancy referred to a comprehensive cancer center

BACKGROUND

Hypercalcemia is a serious and not infrequent complication of malignant diseases; precise information about the incidence of hypercalcemia is not readily available. The study was designed to determine the incidence of hypercalcemia in patients with cancer.

METHODS

Retrospective analysis was done of laboratory data from 7667 patients registered at M.D. Anderson Cancer Center for the first time during 1989 for whom serum calcium levels were determined during the first 2 months after registration.

RESULTS

Severe hypercalcemia (serum calcium level of more than 12.0 mg/100 ml) was present in 40 patients (0.52%); it occurred most often in patients with renal cell cancer (1.42%) and non-small cell lung cancer (1.03%). Less frequent diagnoses were multiple myeloma (0.79%), leukemia (0.63%), non-Hodgkin lymphoma (0.26%), and cancer of the gastrointestinal tract (0.20%). Moderate hypercalcemia (calcium levels of 10.8-12.0 mg/100 ml) was present in 48 patients (0.63%); it occurred most often in patients with renal cell cancer (3.30%) and multiple myeloma (2.38%). Less frequent diagnoses were non-small cell lung cancer (0.89%), non-Hodgkin lymphoma (0.79%), leukemia (0.63%), and cancer of the gastrointestinal tract (0.51%). The presence of hypercalcemia was associated with increased frequency of distant metastases, bone metastases, and increased mortality consistent with other studies of the prognostic effect of this complication.

CONCLUSIONS

Hypercalcemia may appear as a frequent complication in patients with cancer at some time during the course of their disease, but its incidence is relatively low.

Early side-effects of antihypertensive therapy: comparison of amlodipine and nifedipine retard

In a multicentre crossover study of 97 patients with mild hypertension, the incidence and severity of adverse effects were observed during the first 14 days of treatment with amlodipine, nifedipine retard or placebo. Amlodipine (5 mg) once daily was equipotent to nifedipine retard (20 mg) twice daily. At these doses, the incidence of adverse effects was significantly greater during treatment with nifedipine retard (41%) than with amlodipine (27%, P < 0.05) or placebo (16%, P < 0.01). In particular, headache and flushing occurred significantly less frequently during the first 14 days of treatment with amlodipine than with nifedipine retard. The lower incidence and reduced severity of vasodilatory side-effects associated with amlodipine resulted in fewer withdrawals during initiation of therapy (2 on amlodipine compared with 7 on nifedipine retard).

Diuretics in heart failure: some knowns and unknowns

There are many hemodynamic faces of heart failure, ranging from the subclinical to the terminal syndrome. The diuretics possess, with minor qualification, the pharmacotherapeutic attributes of the ideal first-line drug of choice. In heart failure, the loop diuretics have achieved eminence due to their improvement of the deranged hemodynamic profile without significant adverse pharmacologic effects. The new loop diuretics, including torasemide, have been shown to reduce the raised pulmonary vascular pressures without significant depression of the cardiac output in patients with chronic heart failure. This hemodynamic improvement has been paralleled by a significant improvement in clinical symptoms in the majority of patients. The undoubted and widely accepted efficacy of the loop diuretics in all the heart failure syndromes have presented a formidable ethical obstacle to their formal testing in terms of improvement in exercise capacity and reduction of mortality risk. There is still a paucity of information on their singular impact on the excited neuroendocrine reflexes in heart failure and their influence on the widespread metabolic disturbances occasioned by pumping failure of the heart. From the clinical standpoint, however, these deficiencies in information do nothing to reduce the importance of the loop diuretics in the treatment of acute and chronic heart failure.

Vasodilator therapy for acute heart failure: haemodynamic comparison of hydralazine/isosorbide, alpha-adrenoceptor blockade, and angiotensin-converting enzyme inhibition

Haemodynamic comparison of three vasodilation regimens [intravenous (i.v.) hydralazine and isosorbide dinitrate (ISDN) combined, i.v. doxazosin, and i.v. enalaprilat] was undertaken in 36 patients with acute left ventricular (LV) failure due to recent myocardial infarction. Each regimen achieved similar reductions in pulmonary artery occluded pressure (PAOP, preload) and systemic arterial pressures (afterload), with increased cardiac and stroke volume (SV) indexes (p less than 0.01). Only the hydralazine and isosorbide combination induced resting tachycardia. Balanced vasodilatation after selective alpha-adrenoceptor blockade (doxazosin) and angiotensin-converting enzyme (ACE) inhibition (enalaprilat) without increase in heart rate (HR) suggests that these therapies may have definite haemodynamic advantages over the hydralazine/ISDN combination.