Kinetics of congruent vaporization of ZnO islands.

We examine the congruent vaporization of ZnO islands using in situ transmission electron microscopy. Correlating quantitative measurements with a theoretical model offers a comprehensive understanding of the equilibrium conditions of the system, including equilibrium vapor pressure and surface free energy. Interestingly, the surface energy depends on temperature, presumably due to a charged surface at our specific condition of low P and high T. We find that the vaporization temperature decreases with decreasing system size, a trend that is more pronounced at higher T. Applying our results of island decay towards the growth of the ZnO provides new insights into the cooperative facet growth of anisotropic nanocrystals.

Relationship of clinical efficacy to postmortem-determined anatomic subthalamic stimulation in Parkinson syndrome.

OBJECTIVE/BACKGROUND: Patients with medically refractory Parkinson's disease (PD) obtain significant clinical benefit from subthalamic nucleus (STN) stimulation. The degree to which a successful outcome relates to the anatomic location of the stimulating electrode has not yet been clearly established. Many studies have attempted to correlate the clinical result with the electrode location using postoperative magnetic resonance imaging (MRI) and there have been a few that used autopsy-determined locations. In this report, we describe long-term clinical follow-up in a patient with autopsy-determined electrode tip anatomic location. METHODS: A 67-year-old patient with a 27-year history of idiopathic PD complicated by disabling motor fluctuations and dopaminergic dyskinesias underwent bilateral STN deep brain stimulation (DBS). He was prospectively followed in a long-term clinical protocol until his death 40 months after electrode placement. Postoperative magnetic resonance (MR) imaging and postmortem studies of this patient's brain were performed to localize DBS tip locations. RESULTS: STN stimulation produced improvement of the patient's motor fluctuations, dyskinesias and clinical motor performance, especially appendicular tremors, rigidity and bradykinesia. MRI showed the electrode tips to be within 2 mm of the intended target. Postmortem brain analysis identified the right DBS tip location at the dorsomedial edge of the STN, with the left electrode in the vicinity (but not within) the STN. Chronic DBS elicited minor reactive changes were confined to the immediate vicinity of the electrode tracks. The pathological analysis demonstrated numerous cortical Lewy bodies and degenerative encephalopathy, establishing the diagnosis of transitional type diffuse Lewy body disease (DLBD) rather than simple PD. CONCLUSION: This patient obtained clinical benefit from STN stimulation typical of that seen for most PD patients. Both the MR analysis and the autopsy demonstrated electrode placement at or outside the boundaries of the STN, suggesting that that clinical efficacy may not depend on electrode location within the central region of the STN.

Effect of dietary cholesterol on apolipoprotein E synthesis in the rabbit.

Female New Zealand White rabbits were fed either rabbit chow or rabbit chow plus 1% (w/w) cholesterol for 14 days. The chow-fed rabbits had normal plasma lipoprotein profiles on agarose gel electrophoresis, 59 +/- 5 mg of cholesterol and 5.5 +/- 0.4 mg of apolipoprotein E (apoE) per dl of serum. The cholesterol-fed rabbits had significant amounts of beta-VLDL in their serum, 1870 +/- 140 mg of cholesterol and 96 +/- 12 mg of apoE per dl of serum. Relative rates of apoE synthesis were determined by incubating hepatocytes in culture medium containing [3H]leucine for 15 min at 37 degrees C and expressing the radioactivity incorporated into immunoprecipitable apoE as a percentage of the radioactivity incorporated into total protein. Hepatocytes from cholesterol-fed rabbits had twice the relative rate of apoE synthesis (1.05 +/- 0.18%) of hepatocytes from chow-fed rabbits (0.55 +/- 0.07%). This increase in synthesis could be a major contributor to the 17-fold increase in serum apoE levels in the cholesterol-fed rabbit.

Quantitation of apolipoprotein E in rabbit sera with a competitive enzyme-linked immunosorbent assay.

A competitive enzyme-linked immunosorbent assay was developed to quantitate apoE levels in normal and cholesterolemic rabbit serum. The assay can detect 1 ng of apoE and has an interassay coefficient of variation of 5.1%. The assay's antigen specificity was established by the generation of a competitive displacement curve with rabbit apoE, but not with rabbit albumin nor with rabbit apoC. Nonimmune serum was not able to produce a detectable response in the assay. Lipid-protein interactions did not interfere with the assay and color development was linear throughout the incubation time. Rabbits fed a normal diet had 5.3 +/- 0.4 mg of apoE/dl serum. Rabbits fed a diet containing 1% (w/w) cholesterol for 14 days had 86 +/- 11 mg of apoE/dl serum.

Routine cholesterol surveillance in childhood.

Coronary heart disease is the leading cause of death in the United States, and there is reason to believe that it begins in childhood. Evidence is accumulating that early diagnosis and treatment of hypercholesterolemia, a major coronary risk factor, can markedly reduce the incidence of atherosclerotic heart disease in later life. A pediatric group practice consisting of six pediatricians and a pediatric nurse practitioner performed a cholesterol surveillance study of 6500 children between 3 and 18 years of age. Parents and patients were counseled regarding other coronary risk factors, and the American Heart Association diet was recommended. According to the results of the study, 1251 children (19%) exceeded the acceptable 90th percentile for cholesterol and that 143 of 299 significantly hypercholesterolemic children (48%) had no family history of premature myocardial infarction or known hypercholesterolemia. The current recommendation is that only those children from high-risk families should be screened for an elevated cholesterol level. The authors conclude, as a result of this study, that all children older than 3 years of age should have a cholesterol test and that advice regarding avoidance of high-risk coronary life-style behaviors should be a routine part of pediatric anticipatory guidance.

Antimicrobial activity of Visnea mocanera leaf extracts.

A chemical study of Visnea mocanera leaves was carried out giving lupeol and beta-sitosterol fatty esters, as well as beta-sitosterol and the triterpenic betulinic, ursolic, platanic and 2 alpha,3 beta-dihydroxy-ursan-12-en-28-oic and 2 alpha,3 beta-dihydroxy-olean-12-en-28-oic acids. Studies of the antimicrobial activity of acetone and methanol extracts as well as an aqueous infusion were also performed and the good experimental results obtained justify the folk use of this species as a cicatrizant and vulnerary agent.

Essential oils and antimicrobial activity of two varieties of Cedronella canariensis (L.) W. et B.

The qualitative and quantitative determination of the essential oils of the aerial part of two varieties of Cedronella canariensis (L.) W. et B., namely, C. canariensis var. canariensis and C. canariensis var. anisata have been performed, together with the study of the antimicrobial activity of both oils. The noteworthy inhibition exhibited against Bordetella bronchiseptica and Cryptococcus albidus may justify the popular use of the these plants in the treatment of certain diseases of the respiratory tract.

Implications of childhood hypercholesterolemia.

Several studies have documented that hypercholesterolemia is common in American children. Other studies have shown that elevated cholesterol levels in childhood remain elevated well into adult life. Autopsy studies of adolescents have also found a strong positive correlation between antemortem cholesterol levels and early atherosclerotic changes in their aortas and coronary arteries. Collectively, these studies provide strong and consistent evidence that atherosclerosis begins in childhood. The evidence is also overwhelming that lowering elevated low density lipoprotein cholesterol levels reduces the risk of heart attacks caused by coronary heart disease, at least among middle-aged men. As a result, routine cholesterol and coronary heart disease risk factor surveillance in childhood is both productive and appropriate. Premature coronary heart disease may be largely preventable and atherosclerosis, if not preventable, can be significantly delayed.

Influence of cholesterol screening and nutritional counseling in reducing cholesterol levels in children. The American Heart Association.

The purpose of this study was to determine whether cholesterol screening and nutritional counseling can reduce cholesterol concentrations in populations of otherwise unrecognized hypercholesterolemic children. A large pediatric practice in Parma Heights, Ohio, has conducted cholesterol surveillance of children over 2 years of age since 1986. The importance of cholesterol and other recognized risk factors for the progression of atherosclerosis is discussed with all families, and the American Heart Association's Step-One diet is recommended. The present study examines data from a cohort of 894 children (473 boys, 421 girls) who had cholesterol concentrations above 185 mg/dL (4.79 mmol/L) (the 90th percentile) at baseline and, after counseling, had a repeat measurement an average of 2.2 years later. Their mean ages were 7 years at the first testing and 9.2 years at the second. Children who had cholesterol concentrations above 200 mg/dL (5.18 mmol/L) (the 95th percentile) had lipoprotein profiles done, and if their LDL cholesterol exceeded 130 mg/dL (3.37 mmol/L) (the 95th percentile), they were referred to a nutritionist, and family members were advised to have their blood lipids analyzed. Mean cholesterol concentration for all 894 children over this time period decreased by 9.4% (19.5 mg/dL [0.51 mmol/L]; 95% CI = 17.5 mg/dL [0.45 mmol/L] to 21.5 mg/dL [0.56 mmol/L]; P < 0.001). A similar decrease of 8.6% (16.6 mg/dL [0.43 mmol/L); 95% CI = 14.0 mg/dL [0.36 mmol/L] to 19.3 mg/dL [0.50 mmol/L); P < 0.001) was observed for the 463 children who had initial cholesterol concentrations between 185 and 200 mg/dL (4.79 and 5.18 mmol/L) and who therefore received a less intense intervention. Cholesterol concentrations in groups of otherwise unidentified hypercholesterolemic children can be significantly reduced as a result of cholesterol screening and nutritional counseling in a pediatric practice setting.

Randomized, single-blinded comparative study of the efficacy of amoxicillin (40 mg/kg/day) versus standard-dose penicillin V in the treatment of group A streptococcal pharyngitis in children.

A 10-day course of amoxicillin at a dosage of 40 mg per kilogram per day was compared with conventional (lower dosage) penicillin V therapy in the treatment of culture-proven Group A streptococcal pharyngitis in children 3 to 18 years of age in a prospective, randomized, and single-blinded study. Children had to have signs and symptoms compatible with the diagnosis of streptococcal pharyngitis and to have a throat swab positive for Group A streptococci. A second throat culture was obtained 10 to 14 days after the completion of therapy. Serotyping was performed to help differentiate carrier states from reinfections. Of 161 children enrolled, 113 were evaluable; 55 received penicillin and 58 received amoxicillin. At the completion of therapy 70.9% (39/55) of patients in the penicillin group vs 87.9% (51/58) of patients in the amoxicillin group were asymptomatic (clinical cure, P = 0.025). At the completion of therapy, 54.5% (30/55) of patients in the penicillin group vs 79.3% (46/58) of patients in the amoxicillin group had negative throat cultures (bacteriologic cure, P = 0.005). The carrier rate (children who were well but who were still carrying the same serotype of Group A streptococcus) also differed between the groups: 13 (23.6%) in the penicillin group compared with six (10.3%) in the amoxicillin group. Amoxicillin at 40 mg/kg/day was significantly more effective than lower dosages of penicillin V for clinical and bacteriologic cure in the treatment of Group A streptococcal pharyngitis in children. The current perception that penicillin is declining in effectiveness may be due to inadequate dosing.

Effects of bee products on pentylenetetrazole-induced seizures in the rat.

Bee products (BP) have been used for centuries as a diet complement with claimed curative properties. The aim of this study was to determine whether oral administration of BP prevented behavioral, histological, and biochemical alterations, caused by pentylenetetrazole (PTZ)-induced kindling in rats. Male Wistar rats were employed to evaluate seizure latency, number and duration, performance in the open field test, histological alterations and mortality following BP administration. Oral administration of BP at two doses, 30 and 60 mg/kg/day, significantly lengthened latency of both clonic and tonic PTZ-induced seizures, decreased the duration and frequency of seizures and reduced mortality. In the Open Field test, BP treated groups showed increases in the number of crossed squares and rearing counts, and on optimal dose, decreases in fecal boli. Histological analysis showed in PTZ (50 and 80 mg/kg) kindling rats, lungs with inflammatory peribronchiolar, and perialveolar infiltrates. In the liver, mild losses of trabeculae, multi-vesiculated hepatocytes (steatosis) and inflammatory infiltrates in hepatic parenchyma were observed. Interestingly, in the heart, fibers were markedly separated. In testis, stratified epithelium of seminal tubules lost its normal structure, tubules had epithelium loss, spermatids were absent, and spermatogonia and Leydig cells diminished. In PTZ kindling rats treated with BP, the lungs had no inflammatory infiltrates, although the heart showed some inflammatory infiltrates. Remaining structures had normal characteristics. These results, suggest that BP can protect rats from effects of PTZ-induced kindling.

Nanoscale mapping of ion diffusion in a lithium-ion battery cathode.

The movement of lithium ions into and out of electrodes is central to the operation of lithium-ion batteries. Although this process has been extensively studied at the device level, it remains insufficiently characterized at the nanoscale level of grain clusters, single grains and defects. Here, we probe the spatial variation of lithium-ion diffusion times in the battery-cathode material LiCoO(2) at a resolution of ∼100 nm by using an atomic force microscope to both redistribute lithium ions and measure the resulting cathode deformation. The relationship between diffusion and single grains and grain boundaries is observed, revealing that the diffusion coefficient increases for certain grain orientations and single-grain boundaries. This knowledge provides feedback to improve understanding of the nanoscale mechanisms underpinning lithium-ion battery operation.

[Academic performance in the 1st year and its relationship with admission variables in medical schools. Comparative study]. / Rendimiento académico en el primer año y su relación con las variables de ingreso en las escuelas de medicina. Estudio comparativo.

Chilean universities employ a common admission scoring system for students, based on high school grades, mathematic and verbal academic aptitude tests, and specific biology and social sciences tests. Aiming to know the predictive values of these tests, the standardized scores obtained in the selection tests and academic performance of 1094 first year medical students, admitted in 1989 and 1990 to six universities, were analyzed. These students obtained high admission scores and their academic performance during the first year was low (mean grades ranged from 4.6 +/- 0.6 to 5.28 +/- 0.5 in different universities for a scale from 1 to 7). In all, except one university there was a correlation between admission scores and academic performance. Multiple regression analysis showed that admission scores explained a 13% of performance and that the parameters with better predictive value were high school grades, biology test and mathematics academic aptitude test. Verbal academic aptitude test did not have a predictive value.

Therapeutic strategies in the prevention of acute renal failure.

The mechanisms involved and the potentially useful therapeutic strategies in the prevention of acute renal failure (ARF) are briefly reviewed. Factors mentioned are the role of calcium channel blockers, the antioxidant agents, heme oxygenase induction, and ferritin synthesis; and of substances with hemodynamic actions in ARF; such as endothelin, atrial natriuretic peptide, urodilatin, PAF antagonist, prostaglandins, diuretics, and dopamine. The loss of tubular epithelium polarity, the mechanisms involved in this process, and the usefulness of arginine-glycine-aspartic acid peptide and anti-ICAM antibodies in the prevention of tubular obstruction are also reviewed.

Lipoprotein profiles in hypercholesterolemic children.

Atherosclerosis is a process that begins in early life. Coronary heart disease is the result of complex interactions among a variety of risk factors of which hypercholesterolemia is but one. During routine screening, 500 children were identified with total cholesterol levels above the 95th percentile of 5.2 mmol/L (200 mg/dL). Lipoprotein profiles were then performed to confirm and delineate their lipid abnormalities. A definable lipid disorder was present in 85% of such children. Abnormal lipoprotein patterns included 292 children with type IIa, 99 with type IIb, and 25 with type IV phenotypes. An abnormally low high-density lipoprotein cholesterol level of less than 0.9 mmol/L (35 mg/dL) was observed in 20 children. Only 5% of patients were identified as being hypercholesterolemic because they had high-density lipoprotein cholesterol levels above the 95th percentile of 1.8 mmol/L (70 mg/dL). Thirty-two percent of children with total cholesterol levels above 5.2 mmol/L had a family member (sibling, parent, uncle, aunt, or grandparent) with a myocardial infarction prior to 55 years of age. Data from this study support universal cholesterol testing after 3 years of age and lipoprotein profiles for those with levels above 5.2 mmol/L.

[Hypothermia: a non renal indication for peritoneal dialysis]. / Hipotermia: una indicación no renal para la diálisis peritoneal.

Accidental hypothermia, a condition seldomly seen in Chile, is defined as a spontaneous core temperature reduction to less than 35 degrees C and is associated with great morbidity and mortality. We report a 16 years old female intoxicated with liquefied petroleum gas that was admitted in coma, hypothermic, with severe hemodynamic derangement, lactic acidosis, rhabdomyolysis and iliofemoral phlebothrombosis. Peritoneal dialysis with solutions at 27 degrees C was used as a quick and safe means to revert hypothermia and avoid its complications.

Inhibition of steryl glycoside biosynthesis by acyl coenzyme a and by digitonin.

ATP, GTP, CoA, Mg(2+), and Mn(2+) did not inhibit biosynthesis of steryl glycoside and acylated steryl glycoside when added singly to enzyme preparations from spinach leaves. The combination of ATP (but not GTP), CoA, and Mg(2+) or Mn(2+) caused marked inhibition, especially of steryl glycoside biosynthesis, when reaction mixture concentrations of the additions were 0.2 millimolar. Inhibition was attributed to acyl-CoA and could be reproduced by palmitoyl-CoA. The inhibition could be partially prevented by bovine serum albumin. The effects of palmitoyl-CoA were distinct at 10 micromolar, and 50% inhibition of biosynthesis was observed at 40 micromolar.Digitonin (0.6 millimolar) stopped steryl glycoside biosynthesis but permitted the conversion of steryl glycoside to acylated steryl glycoside, thus eliminating the possibility that acylated steryl glycoside is formed from sterol + an acyl-glucose donor.

Partial characterization of steryl ester biosynthesis in spinach leaves.

Acetone powders of a 20,000g pellet fraction from spinach leaves (Spinacia oleracea L.) synthesized [4-(14)C]cholesteryl esters when incubated with [4-(14)C]cholesterol. The reaction was inhibited by digitonin. There was a reciprocal relationship between the decline of label in cholesterol and its incorporation into cholesteryl ester, indicating that free cholesterol was the direct precursor for cholesteryl ester biosynthesis. The hydrolysis of cholesteryl [1-(14)C]palmitate into free cholesterol and [1-(14)C]palmitate was not detected in these acetone powder preparations. Exogenous cholesteryl palmitate had no effect on the esterification of [4-(14)C]cholesterol. The data indicate that an esterase-type mechanism was not involved in the biosynthesis of these steryl esters. Label from [1-(14)C]palmitoyl-CoA was incorporated into steryl esters when incubated with spinach leaf acetone powder preparations. The optimal buffer for steryl ester biosynthesis was 2-(N-morpholino)ethanesulfonate and the optimal pH was 6. Iodoacetamide, N-ethylmaleimide, and dithiothreitol had no effect on the esterification reaction. Ethylenediaminetetraacetate, MgCl(2), CaCl(2), MnCl(2), and ZnSO(4) inhibited at concentrations of 10 to 30 mm.

Subcellular distribution of steryl ester biosynthesis in spinach leaves.

Higher steryl ester biosynthetic activities were obtained with Triton X-100-phosphatidylcholine-cholesterol mixed micelles than with Tween 80-phosphatidylcholine-cholesterol mixed micelles when incubated with spinach leaf (Spinacia oleracea L.) acetone powder preparations. The best incorporation of [4-(14)C]cholesterol into [4-(14)C]cholesteryl ester was obtained with a Triton X-100-phosphatidylcholine-cholesterol (10:1:1, w/w) mixed micelle system. This mixed micelle system, however, required 1,2-dipalmitin and fatty acid-free bovine albumin for optimal activity. The reaction exhibited a diglyceride specificity since the dipalmitin requirement could be replaced with neither 1-monopalmitin nor tripalmitin. Significant amounts of steryl ester biosynthetic activity were detected in the chloroplast (1,000g pellet), mitochondrial (3,000g pellet), and microsomal (20,000g and 88,000g pellet) fractions. Little activity was detected in the water-soluble (88,000g supernatant) fraction. The highest specific activity occurred in the 88,000g pellet. The 88,000g supernatant contained a heatstable, water-soluble substance that was required for optimal steryl ester biosynthesis in all of the pellet fractions. This factor was not lost during extensive dialysis but was destroyed by ashing, indicating that it was large and organic. Silver nitrate thin layer chromatography indicated that 60% of the biosynthesized steryl esters contained saturated fatty acids in the absence of 1,2-dipalmitin and that 83% contained saturated fatty acids in the presence of 1,2-dipalmitin.

Identification of an acyl donor in steryl ester biosynthesis by enzyme preparations from spinach leaves.

A pathway for steryl ester biosynthesis in acetone powder preparations from spinach (Spinacia oleracea L.) leaves has been elucidated; free sterol and 1,2-diglyceride were the substrates. Although animals synthesize cholesteryl esters by three distinct biosynthetic pathways, none of these pathways utilizes 1,2-diglyceride as an acyl donor. Phosphatidylcholine, phosphatidic acid, triglyceride, 1,3-diglyceride, 1-monoglyceride, free fatty acid, and fatty acyl-CoA were not acyl donors for spinach leaf steryl ester biosynthesis in our assay system. The unstable 2 isomer of monoglyceride was not tested. It is possible that 1,2-diglyceride and 2-monoglyceride were both acyl donors for spinach leaf steryl ester biosynthesis. Acyl-labeled phosphatidylcholine and acyl-labeled phosphatidylethanolamine were rapidly degraded by acetone powder preparations to 1,2-diglyceride via phosphatidic acid. The 1,2-diglycerides were slowly metabolized to monoglycerides, triglycerides, free fatty acids, and steryl esters. The monoglycerides were rapidly degraded to free fatty acids and glycerol.