Screening for primary aldosteronism without discontinuing hypertensive medications: plasma aldosterone-renin ratio

The traditional workup for primary aldosteronism is cumbersome and requires discontinuing antihypertensive medications, which is inconvenient and potentially dangerous. A simple and accurate screening test that can be used without modifying medications is needed. The plasma aldosterone-renin ratio (ARR) is a valid screening assay for primary aldosteronism, but antihypertensives are usually discontinued before obtaining this ratio, limiting its utility. The present prospective study is designed to examine the validity of the ARR as a screening test for primary aldosteronism if the ratio is measured randomly while patients continue antihypertensive therapy. During the 18-month study period, 90 patients were referred to the hypertension clinic with poorly controlled hypertension. ARR was measured in random blood samples in all 90 patients while maintaining their prescribed antihypertensive medications. Those with elevated ARRs (>100 ng/dL / ng/mL/h) underwent further diagnostic workup, including adrenal computed tomography and/or magnetic resonance imaging and adrenal iodine 131 norcholesterol uptake scan. Fifteen patients (17%) had elevated ARRs greater than 100:1. Ten of 15 patients were found to have adrenal adenoma on diagnostic workup, and adenoma was later confirmed by histological examination after surgical removal in these 10 patients. Five patients were found to have adrenal hyperplasia; all 5 patients responded to antialdosterone treatment. Thus, all 15 patients had good control of blood pressure after surgery and/or antialdosterone medications. No patient showed a falsely elevated ARR. Data suggest that the ARR is a valid screening assay for primary aldosteronism in patients with poorly controlled blood pressure, and discontinuation of antihypertensive medications is not needed for this test.

Clinical and duplex ultrasound follow-up after balloon angioplasty for atherosclerotic renal artery stenosis

The purpose of this study was to investigate changes in blood pressure and renal function after percutaneous renal artery balloon angioplasty in hypertensive patients with atherosclerotic renal artery stenosis. Renal artery lesions were assessed by duplex ultrasound before and after renal artery balloon angioplasty. Renal arteries were classified as normal, < 60% stenosis, > or =60% stenosis, and occluded according to previously validated duplex criteria. Data regarding risk factors for atherosclerosis and years of hypertension were collected. Systolic and diastolic blood pressure, creatinine, and number of medications were obtained before and after intervention. The immediate technical outcome of renal artery angioplasty was classified based on the arteriographic result as follows: success (residual stenosis < or =30%), partial success (residual stenosis 31-50%), or unsuccessful (residual stenosis > 50%). For bilateral procedures, success required both renal arteries to be classified as technical successes; a technical success on one side only was classified as partial success. The blood pressure response to intervention was classified as follows: cure (diastolic blood pressure < or =95 mm Hg on no medications), improved (control of blood pressure with a significant reduction in number of medications or control of previously elevated blood pressure without a change in medications), or failed (all other responses). The study group included 28 patients (14 men, 14 women) with a mean age of 65 years. The preintervention and the first postintervention evaluations occurred within 180 days of the procedure. All patients were hypertensive, and all except one were under medical treatment. Mean duration of hypertension was 9.1 +/-8.8 years. There were 38 interventional procedures (28 unilateral, 10 bilateral) involving 41 renal arteries; seven arteries had two procedures done. Before angioplasty, all renal arteries had lesions of > or =60% diameter reduction by duplex scanning. Endovascular stents were deployed following angioplasty in 14 (34%) of the procedures. The technical result was classified as a success in 24 (63%), a partial success in 12 (32%) of the procedures, and two procedures (5%) were classed as technical failures. There were statistically significant reductions in blood pressure following successful and partially successful procedures, but cure of hypertension was achieved in only 11% of cases. There were no significant changes in creatinine in any of the technical result groups. Of the 38 renal arteries evaluated with duplex ultrasound following intervention, 39% were found to have stenosis of > or =0% involving a treated renal artery, including one postintervention occlusion. Cure of hypertension was rare in this patient population with atherosclerotic renal artery stenosis. More than one third of the treated renal arteries showed > or =0% lesions recurring after the procedure. Thirteen percent of those with technical success and 17% of those with partial technical success had creatinine improvement of at least 20% over the baseline value. Significant clinical and anatomic improvement were relatively uncommon following balloon angioplasty in this series of patients.

Signal transduction cascades regulating fungal development and virulence

Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

Signal transduction cascades regulating fungal development and virulence

Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

Characterization of the MFalpha pheromone of the human fungal pathogen cryptococcus neoformans

Cryptococcus neoformans is an important human pathogenic fungus with a defined sexual cycle and well-developed molecular and genetic approaches. C. neoformans is predominantly haploid and has two mating types, MATa and MATalpha. Mating is known to be regulated by nutritional limitation and thought also to be regulated by pheromones. Previously, a portion of the MATalpha locus was cloned, and a presumptive pheromone gene, MFalpha1, was identified by its ability to induce conjugation tube-like filaments when introduced by transformation into MATa cells. Here, the ability of the MFalpha1 gene to induce these morphological changes in MATa cells was used as a phenotypic assay to perform a structure-function analysis of the gene. We show that the MFalpha1 open reading frame is required for the morphological response of MATa cells. We also find that the cysteine residue of the C-terminal CAAX motif is required for activity of the MFalpha1 pheromone. In addition, we use a reporter system to measure the expression levels of the MFalpha1 pheromone gene and find that two signals, nutrient starvation and the presence of factors secreted by mating partner cells, impinge on this promoter and regulate MFalpha1 expression. We identify a second pheromone gene, MFalpha2, and show phenotypically that this gene is also expressed. Finally, we have synthesized the MFalpha1 pheromone and show that only the predicted mature modified form of the alpha-factor peptide triggers morphological responses in MATa cells.

Production of halo particles by excitation of collective modes in high-intensity charged particle beams

This paper examines analytically and numerically the effects of self-consistent collective oscillations excited in a high-intensity charged particle beam on the motion of a test particle in the beam core. Even under ideal conditions, assuming a constant transverse focusing force (smooth focusing approximation), and perturbations about a uniform-density, constant radius beam, it is found that collective mode excitations, in combination with the applied focusing force and the equilibrium test fields, can eject particles from the beam core to large radii. Test particle orbits are calculated for collective oscillations with n = 1 and 2 radial mode structure, and an estimate is obtained for the range of initial conditions for which particles will be expelled from the beam interior. Resonances for meridional particles are found to be unimportant, while a class of particles with nonzero angular momentum are found to participate in resonant behavior. Once expelled from the beam, numerical solutions of the orbit equations indicate that Kolmogorov-Arnold-Moser curves, phase space spanning integrals of motion, confine particles within 1.5 times the beam radius for moderately low mode amplitudes, but are successively destabilized for higher amplitudes.

Gene disruption by biolistic transformation in serotype D strains of Cryptococcus neoformans

Gene disruption by biolistic transformation in serotype D strains of Cryptococcus neoformans. Fungal Genetics and Biology 29, 38-48. Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle and well-developed genetic and molecular approaches. Two different transformation systems have been developed, and a number of genes have been disrupted by homologous recombination. However, the frequency of homologous recombination achieved by these approaches has differed dramatically between strains of the A and D serotypes. Transformation by electroporation in serotype D strains results in homologous recombination at frequencies of 1/1000 to 1/100,000, whereas transformation by the biolistic method has resulted in gene disruption at frequencies between 2 and 50% in serotype A strains. We find that gene disruption by homologous recombination can be achieved in the congenic serotype D strain series by biolistic transformation with frequencies of approximately 1 to 4%. By this approach, we have readily disrupted the genes encoding a MAPK homolog (CPK1), the calcineurin A catalytic subunit (CNA1), and a G protein alpha subunit (GPA1). By physical and genetic methods, we show that these mutations result from targeted recombination events without ectopic integrations. Because genetic approaches can be applied in the congenic serotype D strains, our observations represent a significant advance in molecular approaches to understand the physiology and virulence of this important human pathogen.

Molecular analysis of the Cryptococcus neoformans ADE2 gene, a selectable marker for transformation and gene disruption

Cryptococcus neoformans is an important fungal pathogen of man. The incidence of cryptococcal disease has increased dramatically in patients immunocompromised because of HIV infection, organ transplantation, or treatment with cytotoxic chemotherapy or corticosteroids. This organism is an excellent model for molecular dissection of fungal pathogenesis and virulence factors. Here we report the nucleotide sequence of the C. neoformans serotype D genomic ADE2 gene, which encodes a phosphoribosylaminoimidazole carboxylase required for purine biosynthesis. Importantly, this version of the ADE2 gene has been used as the selectable marker for virtually all gene disruptions by transformation and homologous recombination in C. neoformans. We compare the nucleotide and amino acid sequences of the ADE2 gene and product to other highly related adenine biosynthetic genes and enzymes from other yeasts and fungi. We also describe a series of convenient ADE2 cassettes for gene disruption construct preparation. Finally, we have identified the ade2 mutations in strains M001 and M049, adenine auxotrophic mutants derived from the serotype A strain H99. These mutant strains have served as recipients for targeted gene disruptions using the ADE2 gene. These studies should facilitate transformation and gene disruption approaches using the ADE2 selectable marker in this important human fungal pathogen.

Blood pressure, antihypertensive medication, and atherosclerotic renal artery stenosis

The relationship between atherosclerotic renal artery stenosis (ARAS) and blood pressure control remains poorly understood. Duplex ultrasonography is a noninvasive method for detecting and grading ARAS. The purpose of this study was to characterize the relationship between the degree of ARAS, levels of blood pressure, and control of blood pressure with antihypertensive medication. A cross-sectional analysis was performed on 139 patients with ARAS. All patients had at least one diseased renal artery by duplex ultrasound. Renal arteries were classified as normal, less than 60% stenosis, or 60% or greater (high-grade) stenosis. Data regarding blood pressure, coexisting risk factors, and medications were collected. The extent of ARAS was significantly associated with progressive elevation of the systolic blood pressure, whereas the diastolic component was elevated in the case of unilateral high-grade stenosis: no high-grade stenoses, 153 +/- 22/81 +/- 10 mm Hg; unilateral high-grade stenosis, 162 +/- 22/86 +/- 9 mm Hg; and bilateral high-grade stenoses, 174 +/- 27/82 +/- 9 mm Hg (P = 0.002 systolic; P = 0.02 diastolic). Eighty-two percent of the patients were taking known antihypertensive medications. Angiotensin-converting enzyme inhibitor (ACEI) usage versus nonusage was associated with a significantly lower systolic (157 +/- 27 v 169 +/- 22 mm Hg; P = 0.03) and diastolic (79 +/- 9 v 85 +/- 9 mm Hg; P = 0.001) blood pressure. The effect of ACEI usage was observed in patients with high-grade ARAS. None of the other classes of antihypertensive medications were associated with significantly lower blood pressure. In patients with ARAS, blood pressure levels were correlated with the severity of renal artery disease. Patients taking ACEIs had significantly lower blood pressures, and the effect of ACEI usage was strongest among patients with unilateral ARAS.

Prospective study of atherosclerotic disease progression in the renal artery

BACKGROUND

The aim of this study was to determine the incidence of and the risk factors associated with progression of renal artery disease in individuals with atherosclerotic renal artery stenosis (ARAS).

METHODS AND RESULTS

Subjects with >/=1 ARAS were monitored with serial renal artery duplex scans. A total of 295 kidneys in 170 patients were monitored for a mean of 33 months. Overall, the cumulative incidence of ARAS progression was 35% at 3 years and 51% at 5 years. The 3-year cumulative incidence of renal artery disease progression stratified by baseline disease classification was 18%, 28%, and 49% for renal arteries initially classified as normal, <60% stenosis, and >/=60% stenosis, respectively (P=0.03, log-rank test). There were only 9 renal artery occlusions during the study, all of which occurred in renal arteries having >/=60% stenosis at the examination before the detection of occlusion. A stepwise Cox proportional hazards model included 4 baseline factors that were significantly associated with the risk of renal artery disease progression during follow-up: systolic blood pressure >/=160 mm Hg (relative risk [RR]=2.1; 95% CI, 1.2 to 3.5), diabetes mellitus (RR=2.0; 95% CI, 1.2 to 3.3), and high-grade (>60% stenosis or occlusion) disease in either the ipsilateral (RR=1.9; 95% CI, 1.2 to 3.0) or contralateral (RR=1.7; 95% CI, 1.0 to 2.8) renal artery.

CONCLUSIONS

Although renal artery disease progression is a frequent occurrence, progression to total renal artery occlusion is not. The risk of renal artery disease progression is highest among individuals with preexisting high-grade stenosis in either renal artery, elevated systolic blood pressure, and diabetes mellitus.

Carotid and lower extremity arterial disease in patients with renal artery atherosclerosis

BACKGROUND

Atherosclerotic lesions of the carotid and lower extremity arteries may be associated with renal artery stenosis and influence the management of patients with renal artery disease.

OBJECTIVE

To document the prevalence and clinical features of carotid and lower extremity arterial disease in patients with renal artery atherosclerosis.

METHODS

An analysis of baseline data on 149 patients enrolled in a prospective natural history study of atherosclerotic renal artery stenosis. Patients with at least 1 abnormal renal artery by duplex scanning were eligible. Carotid artery disease was evaluated by duplex scanning, and ankle/brachial indices were used to assess the lower extremity arteries. Disease at each of the 3 arterial sites was classified as mild, moderate, or severe based on the extent of involvement on both sides. Serum urea nitrogen, creatinine, and lipid levels were also measured.

RESULTS

Severe renal, carotid, or lower extremity arterial disease was present in 44%, 19%, and 21% of the patients, respectively. There was a trend for patients with increasing degrees of renal artery disease to have increasing degrees of carotid and lower extremity arterial disease. The prevalence of severe carotid artery disease increased from 7% in the mild renal artery group to 28% in the severe renal artery group. Clinical factors that were most predictive of severe disease were elevated apolipoprotein B levels for the renal arteries, high serum urea nitrogen or creatinine levels for the carotid arteries, and smoking for the lower extremity arteries.

CONCLUSIONS

There was a strong association between severe renal artery atherosclerosis and severe carotid artery disease. Patients with renal artery disease also had a high prevalence of lower extremity arterial disease. In this patient population, screening for lower extremity arterial disease can be reserved for those with signs or symptoms of peripheral ischemia. Noninvasive carotid screening is justified in patients with renal artery disease to detect asymptomatic lesions that require either immediate surgical treatment or serial follow-up for disease progression.

Risk of atrophy in kidneys with atherosclerotic renal artery stenosis

The goal of this study was to determine the incidence of and risk factors for renal atrophy among kidneys with atherosclerotic renal artery stenosis (ARAS). Participants with at least one ARAS were followed prospectively with duplex scans performed every six months. Renal atrophy was defined as a reduction in renal length of greater than 1 cm. A total of 204 kidneys in 122 subjects were followed for a mean of 33 months. The two-year cumulative incidence (CI) of renal atrophy was 5.5%, 11.7%, and 20.8% in kidneys with a baseline renal artery disease classification of normal, <60% stenosis, and > or = 60% stenosis, respectively (P = 0.009, log rank test). Other baseline factors associated with a high risk of renal atrophy included a systolic blood pressure > 180 mm Hg (2-year CL = 35%, P = 0.01), a renal artery peak systolic velocity > 400 cm/second (2-year CI = 32%, P = 0.02), and a renal cortical end diastolic velocity < or = 5 cm/second (2-year CI = 29%, P = 0.046). The number of kidneys demonstrating atrophy per participant was correlated with elevations in the serum creatinine concentration (P = 0.03). In patients with ARAS, there is a significant risk of renal atrophy among kidneys exposed to elevated systolic blood pressure and among those with high-grade ARAS and low renal cortical blood flow velocity as assessed by renal duplex scanning. The occurrence of renal atrophy is well-correlated with changes in the serum creatinine concentration.