Hypertension in Latin America: Current perspectives on trends and characteristics.

The region of Latin America, which includes Central America, the Caribbean and South America, is one that is rapidly developing. Signified by socio-economic growth, transition and development over the last few decades, living standards in countries like Brazil and Mexico have improved dramatically, including improvements in education and health care. An important marker of socio-economic change has been the epidemiological shift in disease burden. Cardiovascular disease is now the leading cause of death in Latin America, and the drop in prevalence of infectious diseases has been accompanied by a rise in non-communicable diseases. Hypertension is the major risk factor driving the cardiovascular disease continuum. In this article we aim to discuss the epidemiological and management trends and patterns in hypertension that may be specific or more common to Latin-American populations - what we term 'Latin American characteristics' of hypertension - via a review of the recent literature. Recognizing that there may be a specific profile of hypertension for Latin-American patients may help to improve their treatment, with the ultimate goal to reduce their cardiovascular risk. We focus somewhat on the countries of Brazil, Mexico and Venezuela, the experience of which may reflect other Latin American countries that currently have less published data regarding epidemiology and management practices.

How to Convert SPME to P3M: Influence Functions and Error Estimates.

We demonstrate explicitly how the two seemingly different particle mesh Ewald methods, the smooth particle mesh Ewald (SPME) and the particle-particle particle mesh (P3M), can be mathematically transformed into each other. This allows us in particular to convert the error estimate of the P3M method in the energy-conserving scheme (also known as "P3M with analytic differentiation") into an error estimate for the SPME method, via a simple change of the lattice Green function. Our error estimate is valid for any values of the SPME parameters (mesh size, spline interpolation order, Ewald splitting parameter, real-space cutoff distance), including odd orders of splines. The problem with the self-forces is avoided thanks to an analytical formula that allows to subtract them directly within the particle mesh calculation. Plots of the accuracy of the SPME forces are provided for a wide range of parameter values. The main use of the error estimate is to allow a simulation program to scan quickly the multidimensional parameter space to find the best set of parameters to achieve a target accuracy at the smallest computational cost. As a byproduct, we show how a SPME code can be transformed into a P3M version by changing a few lines of code. We demonstrate also that the P3M lattice Green function can be approximated by a closed form expression, computable on-the-fly, that provides essentially the same accuracy as the full function.

Simulations of non-neutral slab systems with long-range electrostatic interactions in two-dimensional periodic boundary conditions.

We introduce a regularization procedure to define electrostatic energies and forces in a slab system of thickness h that is periodic in two dimensions and carries a net charge. The regularization corresponds to a neutralization of the system by two charged walls and can be viewed as the extension to the two-dimensional (2D)+h geometry of the neutralization by a homogeneous background in the standard three-dimensional Ewald method. The energies and forces can be computed efficiently by using advanced methods for systems with 2D periodicity, such as MMM2D or P3M/ELC, or by introducing a simple background-charge correction to the Yeh-Berkowitz approach of slab systems. The results are checked against direct lattice sum calculations on simple systems. We show, in particular, that the Madelung energy of a 2D square charge lattice in a uniform compensating background is correctly reproduced to high accuracy. A molecular dynamics simulation of a sodium ion close to an air/water interface is performed to demonstrate that the method does indeed provide consistent long-range electrostatics. The mean force on the ion reduces at large distances to the image-charge interaction predicted by macroscopic electrostatics. This result is used to determine precisely the position of the macroscopic dielectric interface with respect to the true molecular surface.

The optimal P3M algorithm for computing electrostatic energies in periodic systems.

We optimize Hockney and Eastwood's particle-particle particle-mesh algorithm to achieve maximal accuracy in the electrostatic energies (instead of forces) in three-dimensional periodic charged systems. To this end we construct an optimal influence function that minimizes the root-mean-square (rms) errors of the energies. As a by-product we derive a new real-space cutoff correction term, give a transparent derivation of the systematic errors in terms of Madelung energies, and provide an accurate analytical estimate for the rms error of the energies. This error estimate is a useful indicator of the accuracy of the computed energies and allows an easy and precise determination of the optimal values of the various parameters in the algorithm (Ewald splitting parameter, mesh size, and charge assignment order).

Adsorption of semiflexible block copolymers on homogeneous surfaces.

We present the results of extensive numerical off-lattice Monte Carlo simulations of semiflexible block-copolymer chains adsorbed onto flat homogeneous surfaces. We have compared the behavior of several chain structures, such as homopolymers, diblocks, (A(alpha)B(alpha)) block copolymers, and random heteropolymers. In all the cases studied, we have found the adsorption process to be favored with an increase of the chain rigidity. Particularly, the adsorption of diblock structures becomes a two-step process characterized by two different adsorbing temperatures that depend on the chain stiffness kappa, the chain length N, and the adsorbing energies epsilon(A) and epsilon(B). This twofold adsorbing process changes to a single one for copolymers of reduced block size alpha. Each block of the stiff copolymer chain is found to satisfy the classical scaling laws for flexible chains, however, we found the scaling exponent phi to depend on the chain stiffness. The measurement of the radius of gyration exhibits a typical behavior of a polymer chain composed of Nl(p) blobs whose persistence length follows l(p) approximately (kappa/k(B)T)(0.5) for large stiff chains.

Methylenetetrahydrofolate reductase mutation (677C-->T) negatively influences plasma homocysteine response to marginal folate intake in elderly women.

Individuals who are homozygous for the methylenetetrahydrofolate reductase (MTHFR) 677C --> T mutation have depressed serum folate (SF) and elevated plasma total homocysteine (tHcy) concentrations, which may affect folate requirements and increase the risk for coronary artery disease. A controlled metabolic study (14 weeks) using a depletion/repletion protocol was performed in women (aged 60 to 85 years, N = 33) to provide age-specific data on the effects of the MTHFR mutation on SF and tHcy status. Subjects consumed a moderately folate-deplete diet (118 microg/d) for 7 weeks, followed by 7 weeks of folate repletion with 200 or 415 microg/d provided as two different treatments. Following folate depletion, the mean SF concentration was lower for homozygous (P = .017) versus heterozygous subjects. Homozygotes for the 677C --> T mutation showed a higher (P = .015) percent increase in plasma tHcy (44%) than heterozygous (20%) or normal (15%) subjects. At week 7, the mean plasma tHcy concentration was higher in homozygous subjects (12.5 +/- 5.3 micromol/L, mean +/- SD) versus the heterozygous (10.8 +/- 3.8 micromol/L, P = .008) or normal (11.3 +/- 2.7 micromol/L, P = .001) genotype groups. Following folate repletion, plasma tHcy concentrations were not different between genotype groups, despite a higher (P < .016) SF concentration in subjects with the homozygous genotype. These data suggest that older women who are homozygous for the MTHFR 677C --> T mutation may be at risk for greater elevations in plasma tHcy in response to moderately low folate intake as compared with individuals with the normal or heterozygous genotypes.

Genomic DNA methylation decreases in response to moderate folate depletion in elderly women.

BACKGROUND: Methylation of genomic DNA is dependent on an adequate supply of folate coenzymes. Previous data support the hypothesis that abnormal DNA methylation plays an integral role in carcinogenesis. To date, no studies assessing the effect of inadequate folate status on DNA methylation in older women (aged >63 y) have been reported. OBJECTIVE: The effect of moderate folate depletion followed by folate repletion on leukocyte genomic DNA methylation was investigated in elderly women (aged 60-85 y) to evaluate whether DNA methylation could be used as a functional indicator of folate status. DESIGN: Healthy, postmenopausal women (n = 33) consumed a moderately folate-depleted diet (118 microg folate/d) for 7 wk, followed by 7 wk of folate repletion with 200 or 415 microg/d, each provided as 2 different dietary treatments for a total of 4 treatment groups (n = 30). Leukocyte DNA methylation was determined on the basis of the ability of DNA to incorporate [(3)H]methyl groups from labeled S:-adenosylmethionine in an in vitro assay. RESULTS: Incorporation of [(3)H]methyl groups increased significantly (P: = 0.0025) in response to folate depletion, suggesting undermethylation of DNA. No significant changes were detected in [(3)H]methyl incorporation in any group over the 7-wk repletion period compared with postdepletion values. CONCLUSIONS: DNA methylation status may be used as a functional indicator of moderately depleted folate status. The slow response to the repletion diets observed suggests that normalization of DNA methylation after moderate folate depletion may be delayed in older women.

Remedial education: can this doctor be saved?

In the first two years of the program 30 physicians have completed the program. A list of the distribution of specialties/practice areas [table: see text] served is provided in Table 1. The data reveal that the distribution of practice areas corresponds approximately to the distribution of physicians practicing in the state. The UF C.A.R.E.S Program provides a great benefit to physicians and their patients. It provides an atmosphere of professional collaboration and encouragement to address specific educational needs and underscores a commitment to providing continuing medical education, meaningful doctor-to-doctor collaboration, better patient care, and reflects a medical model of diagnosis and treatment of specific problems.

Folate status of elderly women following moderate folate depletion responds only to a higher folate intake.

Dietary Reference Intakes (DRI) for folate for elderly women have been based primarily on data extrapolated from studies in younger women. This study was conducted to provide the first age-specific data in elderly women (60-85 y) from a controlled metabolic study on which to base folate intake recommendations. Subjects (n = 33) consumed a moderately folate-deplete (118 microg/d) diet for 7 wk, followed by repletion diets providing either 200 or 415 microg folate/d as diet plus folic acid (FA) or a combination of FA and orange juice (OJ) for 7 wk (n = 30). Comparisons among and within groups were made for serum folate (SF), RBC folate and plasma total homocysteine (tHcy) concentrations. SF concentrations decreased significantly (P < 0.001) during depletion (65 +/- 15%). Postrepletion, the adjusted SF concentration for subjects consuming 415 microg folate/d was significantly greater (P = 0.003) than for subjects consuming 200 microg folate/d. RBC folate concentrations decreased (P < 0.001) during depletion (21 +/- 10%) and further (P < 0.001) during repletion (5 +/- 14%). During depletion, plasma tHcy concentrations increased significantly (P < 0.001) and an inverse relationship between SF and plasma tHcy concentrations was observed in 94% of subjects (P < 0.001). Reversal of this inverse relationship was significant only for subjects consuming 415 microg folate/d (P < 0.001). Postrepletion, subjects consuming 200 microg folate/d had a significantly higher (P = 0.009) adjusted plasma tHcy concentration than subjects consuming 415 microg folate/d. These data in elderly women indicate that 415 microg/d folate, provided as a combination of diet, FA and OJ, or diet and FA, normalizes folate status more effectively than does 200 microg/d, thus providing age-specific data for future folate intake recommendations.

Enteral nutrition in clinical practice.

Enteral nutrition has, at long last, found its place in the modulation of disease. Because of its importance in terms of both anabolic and catabolic processes, today's clinician must have a working knowledge of the types of enteral formulations, their delivery and the therapeutic considerations (particularly concomitant medications) that impact on the safety and efficacy of enteral nutrition. The advantages and disadvantages of this therapeutic intervention must be carefully weighed by the clinician, in concert with sound medical principles. Despite the widespread belief that enteral nutrition is superior to parenteral nutrition in humans, data does suggest that there is little difference between the two. Also, associated costs of enteral nutrition in contrast to parenteral nutrition need to be reappraised based on more invasive enteral access and falling parenteral nutrition prices. Although the enteral route is presumed to be the best feeding modality, the clinician must be ever vigilant about the shortcomings of using the gut, especially in the setting of severe inflammation, stenosis or sepsis. The best feeding modality, then, must blend a knowledge of the patients' anatomy, physiology, and disease with considerations of enteral access, timing of delivery, complications, and a myriad of other therapeutic variables (to include concurrent medication administration) that impact on the enteral feeding regimen. This article reviews the basic principles of enteral nutrition in clinical practice. It describes nutritional assessment, routes of administration, selection of feeding formulas based on nutritional needs, interactions with medications, as well as possible complications of enteral feeding.

Irritable bowel syndrome. Streamlining the diagnosis.

IBS is one of the most common of the gastrointestinal disease, but it can be a diagnostic challenge because of the many symptoms that overlap with other such diseases. Most common among the symptoms are abdominal pain, a feeling of intestinal distention or bloating, and either diarrhea or constipation. Patients may be found to have an exacerbation of symptoms with stress, and they may have an increased sensitivity to bowel distention. History and physical examination findings often can be relied on to make the diagnosis, avoiding overuse of laboratory testing. Treatment consists of patient education and support, lifestyle and dietary changes, and use of several pharmacologic agents for symptom relief. Antidepressants are being investigated as a possible additional form of treatment.

Chronic diarrhea associated with thymoma and hypogammaglobulinemia (Good's syndrome).

We report the case of a patient with severe diarrhea and malabsorption who was subsequently found to have hypogammaglobulinemia and thymoma (Good's syndrome). The mechanism by which hypogammaglobulinemia and/or thymoma causes diarrhea is unclear. It may be related to malabsorption caused by a mucosal lesion resembling villous atrophy, which may resolve with restoration of immunologic status. Diarrhea in some patients may respond to commercial gamma globulin injections, fresh frozen plasma, or cholestyramine therapy. The etiologic relationship between thymoma and acquired hypogammaglobulinemia remains unclear. Thymectomy is generally ineffective in improving immunologic deficiencies and coexisting conditions in patients with acquired hypogammaglobulinemia. In our patient's case, severe diarrhea resolved after resection of the thymoma.

Rectal perflubron: new application in MRI of perirectal fistulae.

PURPOSE: Our goal was to determine the efficacy of MRI with rectal administration of perflubron in the evaluation of perirectal and pelvic fistulae, with an emphasis on development of an improved method for fistula visualization. METHOD: Fourteen pelvic and/or perirectal fistulae were evaluated in nine patients with MRI after the rectal administration of 200 ml of perflubron. Images were reviewed by two independent readers and evaluated for the presence or absence of fistulae. Qualitative assessment was also performed, rating the examinations for the ability to visualize the fistulae. Comparison was made with the clinical examination and/or operative findings, as well as available preperflubron imaging studies (CT = 10; fluoroscopy = 1; preperflubron MRI = 4). RESULTS: MRI with rectal perflubron demonstrated all 14 fistulae (100%), while preperflubron imaging demonstrated only 7 of 14 (50%) fistulae (p < or = 0.008, Wilcoxon signed rank test). In addition, MRI with perflubron resulted in significantly improved qualitative visualization of fistulae (overall very good rating versus poor rating for preperflubron imaging, p < or = 0.006, Wilcoxon signed rank test). CONCLUSION: MRI with rectal perflubron is a superior modality for imaging of fistulae, compared with conventional methods, since it allows a noninvasive means of demonstrating the presence of a fistula as well as offers improved qualitative assessment of fistulous disease.

Benefits of dietary fiber. Myth or medicine?

In recent years, many health claims have been made about dietary and supplemental fiber. However, some reports (eg, those regarding oat bran) have been controversial. A review of scientifically rigorous studies shows that fiber has some preventive or therapeutic benefits in irritable bowel syndrome, diverticulosis, colorectal cancer, diabetes, and hypercholesterolemia. However, it appears to have no direct benefit in patients with inflammatory bowel disease, gallstones, or obesity. The United States has one of the lowest per capita intakes of fiber in the world. Therefore, increasing daily fiber intake either through diet or with supplements is recommended for most Americans. Consumer interest groups should lobby for more fiber-enriched foods. The challenge for education and healthcare professionals alike is to remold the nation's interest in and understanding of dietary fiber.

Dietary fiber: fact and fiction.

There have been many conflicting reports about the benefits of dietary fiber. Dietary fiber has been touted to provide remarkable benefits: from the control of functional bowel disease to the prevention of cancer. We have reviewed all prominent studies on the benefits of dietary fiber and examined the nature of their conflicting results. Recommendations for dietary fiber intake are also discussed.

Controlled dietary folate affects folate status in nonpregnant women.

In a study designed to estimate the requirement for dietary folate in nonpregnant women, 17 women (21-27 y) consumed 200, 300, or 400 micrograms/d of total folate for 70 d which was provided by low folate conventional foods (30 micrograms) plus supplemental folic acid. Group means for initial serum and erythrocyte folate and plasma homocysteine concentrations were not significantly different. Serum and erythrocyte folate decreased relative to the initial value in the 200 micrograms/d group (43.4 +/- 12.1%, 13.6 +/- 16.6%, respectively; mean +/- SD), in contrast to an increase in the 400 micrograms/d group (16.8 +/- 52.0%, 10.2 +/- 18.5%, respectively). The final serum folate in the 200 and 300 micrograms/d groups (6.4 +/- 0.8 nmol/L, 7.3 +/- 1.1 nmol/L, respectively) was significantly lower than that of the 400 micrograms/d group (14.3 +/- 2.0 nmol/L), with evidence in the 200 micrograms/d and 300 micrograms/d groups of low ( < 6.8 nmol/L) serum folate concentrations. Differences in final erythrocyte folate did not reach statistical significance, although low values ( < 362 nmol/L) were frequent in subjects with 200 micrograms/d intake. In the 200 micrograms/d group, plasma homocysteine was negatively correlated with serum and erythrocyte folate, and final mean plasma homocysteine (12.6 +/- 1.7 mumol/L) was significantly higher than that of the 300 or 400 micrograms/d groups. Elevated plasma homocysteine levels ( > 16 mumol/L) were observed in the 200 micrograms/d group only.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of atherosclerosis by dietary pectin in microswine with sustained hypercholesterolemia.

Sustained hypercholesterolemia is a known risk factor for development of atherosclerosis. In animal studies, grapefruit pectin fed concurrently with a high-lipid diet inhibits hypercholesterolemia and atherogenesis. The purpose of the present study was to determine if grapefruit pectin affects cholesterol levels and atherogenesis of animals with established hypercholesterolemia. Microswine were fed an atherogenic diet to establish hypercholesterolemia. Plasma cholesterol levels rose rapidly and for 360 days were sustained at levels 6- to 12-fold the normal level. Then, half the microswine, selected at random, were fed a diet in which 3% grapefruit pectin was substituted for cellulose, and the remaining animals received the original diet. Animals were killed 270 days later, and the extent of atherosclerosis was determined. In animals with established hypercholesterolemia, pectin did not lower their cholesterol levels. However, pectin reduced the extent of atherosclerosis in both the aorta and coronary arteries. The mean surface area covered by atherosclerosis in the aorta was 13.6% in the group that did not receive pectin compared with 5.3% in the group that did receive pectin. The mean coronary artery narrowing was 45% without pectin and 24% with pectin. We conclude that pectin may have a direct beneficial effect on atherosclerosis by a mechanism independent of cholesterol levels.

The gerbil, hamster, and guinea pig as rodent models for hyperlipidemia.

The purpose of this study was to compare the effects of a hyperlipidemic diet on three different rodent models to evaluate them on how their responses simulate human serum lipid diseases. Forty hamsters, 40 gerbils, and 20 guinea pigs were given either a chow diet or a modified high-fat, high-cholesterol diet (HF/HC) for 7 days. Food was withheld from half of the animals on each diet for 12 hours prior to collecting the blood for analysis of total cholesterol and triglyceride concentration. In all species, HF/HC feeding resulted in at least a 370% increase in total cholesterol concentration. Withholding food significantly decreased total cholesterol concentration in hamsters and gerbils fed HF/HC but had no effect on animals fed chow diet. Triglyceride concentrations were increased by the HF/HC in the hamster and the gerbil. As with total cholesterol, triglyceride concentration was decreased after food was withheld in these two animal groups. We suggest that the guinea pig is the most appropriate model for studying hypercholesterolemia because of its moderate plasma cholesterol response and normal triglyceride response to a HF/HC. We also suggest that the hamster is a good model for studying hypertriglyceridemia since increased serum triglyceride concentrations can be easily maintained on a HF/HC.