Esofagitis linfocítica: una causa rara emergente de impactación alimentaria / Lymphocytic oesophagitis: a rare emerging cause of food impaction

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Randomised clinical trial: the analgesic properties of dietary supplementation with palmitoylethanolamide and polydatin in irritable bowel syndrome.

BACKGROUND: Intestinal immune activation is involved in irritable bowel syndrome (IBS) pathophysiology. While most dietary approaches in IBS involve food avoidance, there are fewer indications on food supplementation. Palmithoylethanolamide, structurally related to the endocannabinoid anandamide, and polydatin are dietary compounds which act synergistically to reduce mast cell activation. AIM: To assess the effect on mast cell count and the efficacy of palmithoylethanolamide/polydatin in patients with IBS. METHODS: We conducted a pilot, 12-week, randomised, double-blind, placebo-controlled, multicentre study assessing the effect of palmithoylethanolamide/polydatin 200 mg/20 mg or placebo b.d. on low-grade immune activation, endocannabinoid system and symptoms in IBS patients. Biopsy samples, obtained at screening visit and at the end of the study, were analysed by immunohistochemistry, enzyme-linked immunoassay, liquid chromatography and Western blot. RESULTS: A total of 54 patients with IBS and 12 healthy controls were enrolled from five European centres. Compared with controls, IBS patients showed higher mucosal mast cell counts (3.2 ± 1.3 vs. 5.3 ± 2.7%, P = 0.013), reduced fatty acid amide oleoylethanolamide (12.7 ± 9.8 vs. 45.8 ± 55.6 pmol/mg, P = 0.002) and increased expression of cannabinoid receptor 2 (0.7 ± 0.1 vs. 1.0 ± 0.8, P = 0.012). The treatment did not significantly modify IBS biological profile, including mast cell count. Compared with placebo, palmithoylethanolamide/polydatin markedly improved abdominal pain severity (P < 0.05). CONCLUSIONS: The marked effect of the dietary supplement palmithoylethanolamide/polydatin on abdominal pain in patients with IBS suggests that this is a promising natural approach for pain management in this condition. Further studies are now required to elucidate the mechanism of action of palmithoylethanolamide/polydatin in IBS. ClinicalTrials.gov number, NCT01370720.

The joint power of sex and stress to modulate brain-gut-microbiota axis and intestinal barrier homeostasis: implications for irritable bowel syndrome.

BACKGROUND: Intestinal homeostasis is a dynamic process that takes place at the interface between the lumen and the mucosa of the gastrointestinal tract, where a constant scrutiny for antigens and toxins derived from food and microorganisms is carried out by the vast gut-associated immune system. Intestinal homeostasis is preserved by the ability of the mucus layer and the mucosal barrier to keep the passage of small-sized and antigenic molecules across the epithelium highly selective. When combined and preserved, immune surveillance and barrier's selective permeability, the host capacity of preventing the development of intestinal inflammation is optimized, and viceversa. In addition, the brain-gut-microbiome axis, a multidirectional communication system that integrates distant and local regulatory networks through neural, immunological, metabolic, and hormonal signaling pathways, also regulates intestinal function. Dysfunction of the brain-gut-microbiome axis may induce the loss of gut mucosal homeostasis, leading to uncontrolled permeation of toxins and immunogenic particles, increasing the risk of appearance of intestinal inflammation, mucosal damage, and gut disorders. Irritable bowel syndrome is prevalent stress-sensitive gastrointestinal disorder that shows a female predominance. Interestingly, the role of stress, sex and gonadal hormones in the regulation of intestinal mucosal and the brain-gut-microbiome axis functioning is being increasingly recognized. PURPOSE: We aim to critically review the evidence linking sex, and stress to intestinal barrier and brain-gut-microbiome axis dysfunction and the implications for irritable bowel syndrome.

An optimization based on simulation approach to the patient admission scheduling problem using a linear programing algorithm.

BACKGROUND: As patient's length of stay in waiting lists increases, governments are looking for strategies to control the problem. Agreements were created with private providers to diminish the workload in the public sector. However, the growth of the private sector is not following the demand for care. Given this context, new management strategies have to be considered in order to minimize patient length of stay in waiting lists while reducing the costs and increasing (or at least maintaining) the quality of care. METHOD: Appointment scheduling systems are today known to be proficient in the optimization of health care services. Their utilization is focused on increasing the usage of human resources, medical equipment and reducing the patient waiting times. In this paper, a simulation-based optimization approach to the Patient Admission Scheduling Problem is presented. Modeling tools and simulation techniques are used in the optimization of a diagnostic imaging department. RESULTS: The proposed techniques have demonstrated to be effective in the evaluation of diagnostic imaging workflows. A simulated annealing algorithm was used to optimize the patient admission sequence towards minimizing the total completion and total waiting of patients. The obtained results showed average reductions of 5% on the total completion and 38% on the patients' total waiting time.

Control de la hemostasia durante la nefrectomía parcial laparoscópica sin renorrafia parenquimatosa: la experiencia Vivostat ® / Haemostasis Control during Laparoscopic Partial Nephrectomy without Parenchymal Renorrhaphy: the VIVOSTAT® Experience

Objetivo: Presentar nuestra experiencia en el control hemostático de la nefrectomía parcial laparoscópica utilizando un compuesto de fibrina autóloga (Vivostat system®), sin reconstrucción del parénquima renal. Material y métodos: Hemos realizado 45 nefrectomías parciales utilizando este agente hemostático. Los principales pasos quirúrgicos fueron: decolación, identificación del uréter, hilio y tumoración renal, control de la arteria renal con torniquete de Rummel, exéresis tumoral con bisturí armónico y aplicación del sellador de fibrina en el lecho quirúrgico en 2 fases (antes y después de la reperfusión renal). Se registraron datos de sangrado precoz o diferido. Resultados: Edad media: 63,9 años (33-80); tamaño medio del tumor 2,5cm (1,5-4); tiempo medio quirúrgico: 136,1minutos (90-180). Tiempo medio de isquemia caliente 19,2minutos (10-30). Pérdida sanguínea media: 97ml (50-300). Se realizaron puntos hemostáticos individuales antes de la aplicación del sellador de fibrina, en caso de sangrado activo importante (14 casos). No se registró ningún caso de sangrado ni fallo renal en el postoperatorio. Un paciente requirió transfusión sanguínea debido a gran hematoma en pared abdominal. El 65% fue carcinoma de célula clara renal, el 10% carcinoma papilar y un 20% fueron oncocitomas. La tasa de márgenes negativos fue del 100%. El tiempo medio de ingreso hospitalario fue 4 días (2-6). El seguimiento medio fue de 14 meses (5-45). Conclusiones: Excluir la renorrafia durante la nefrectomía parcial laparoscópica es posible y seguro. Nuestra experiencia inicial con este sellador de fibrina ha sido positiva, aunque probablemente se necesiten más casos y seguimiento para determinar el beneficio de esta técnica quirúrgica (AU)

Objective: To present our experience using an autologous fibrin sealant prepared with the Vivostat system® to control haemostasis without any renal parenchymal reconstruction. Material and methods: We performed 45 laparoscopic partial nephrectomies using this haemostatic agent. The surgical steps were: colon mobilization, identification of ureter, renal vessels and renal tumor, renal artery control with Rummel tourniquet, tumor excision with harmonic scalpel, application of fibrin glue to the resection bed twice (before and after kidney reperfusion). Patients were evaluated for acute or delayed bleeding. Results: Mean age was 63.9 years (33-80); mean tumor size was 2.5cm (1.5-4); mean operative time was 136.1min (90-180). Mean warm ischemia time was 19.2min (10-30). Mean blood loss was 97ml (50-300). Individual haemostatic stitches were performed before application of the sealant if acute bleeding was observed (14 cases). We did not achieve any case of postoperative bleeding from resection bed or renal failure. 1 patient required transfusion due to an abdominal wall haematoma. 65% were clear cell carcinoma, 10% were papillary carcinoma, 20% were oncocitoma. Free margin rate was 100%. Mean hospital stay was 4 days (2-6). Mean follow-up was 14 months (5-45). Conclusions: Excluding renorrhaphy during laparoscopic partial nephrectomy is feasible and safe. Our initial experience with the vivostat system in laparoscopic partial nephrectomy has been encouraging, but longer follow-up is needed to determine the real benefit of this surgical technique in laparoscopic partial nephrectomy (AU)

[Haemostasis control during laparoscopic partial nephrectomy without parenchymal renorrhaphy: the VIVOSTAT(®) experience]. / Control de la hemostasia durante la nefrectomía parcial laparoscópica sin renorrafia parenquimatosa: la experiencia Vivostat(®).

OBJECTIVE: To present our experience using an autologous fibrin sealant prepared with the Vivostat system(®) to control haemostasis without any renal parenchymal reconstruction. MATERIAL AND METHODS: We performed 45 laparoscopic partial nephrectomies using this haemostatic agent. The surgical steps were: colon mobilization, identification of ureter, renal vessels and renal tumor, renal artery control with Rummel tourniquet, tumor excision with harmonic scalpel, application of fibrin glue to the resection bed twice (before and after kidney reperfusion). Patients were evaluated for acute or delayed bleeding. RESULTS: Mean age was 63.9 years (33-80); mean tumor size was 2.5cm (1.5-4); mean operative time was 136.1min (90-180). Mean warm ischemia time was 19.2min (10-30). Mean blood loss was 97ml (50-300). Individual haemostatic stitches were performed before application of the sealant if acute bleeding was observed (14 cases). We did not achieve any case of postoperative bleeding from resection bed or renal failure. 1 patient required transfusion due to an abdominal wall haematoma. 65% were clear cell carcinoma, 10% were papillary carcinoma, 20% were oncocitoma. Free margin rate was 100%. Mean hospital stay was 4 days (2-6). Mean follow-up was 14 months (5-45). CONCLUSIONS: Excluding renorrhaphy during laparoscopic partial nephrectomy is feasible and safe. Our initial experience with the vivostat system in laparoscopic partial nephrectomy has been encouraging, but longer follow-up is needed to determine the real benefit of this surgical technique in laparoscopic partial nephrectomy.

Double-balloon jejunal perfusion to compare absorption of vitamin E and vitamin E acetate in healthy volunteers under maldigestion conditions.

BACKGROUND/OBJECTIVES: The vitamin E derivative, α-tocopheryl acetate, is often included in formulations used in enteral nutrition. In this respect, we compared α-tocopherol and α-tocopheryl acetate absorption under 'maldigestion' conditions, such as occurring during enteral tube feeding, using differentially labeled RRR-[5,7-methyl-((2)H(6))]-α-tocopherol and RRR-[5-methyl-(2)H(3)]-α-tocopheryl acetate allowing direct comparison between free and esterified forms. SUBJECTS/METHODS: The two derivatives were given together in a single dose to six volunteers directly into the jejunum using a double-balloon perfusion system. Perfusion lasted for 1 h, and the collected blood and effluent samples were analyzed by liquid chromatography-mass spectrometry. RESULTS: In the isolated 20-cm length of exposed jejunum, on average ~ 6% of the two vitamin E forms were absorbed >1 h based on subtraction of effluent from influent. There was substantial difference in the absolute absorbed quantity between individuals, but no significant differences were observed in the absorption between the two labeled forms as assessed in the plasma. (2)H(3)-α-tocopherol was not present in the influent, but appeared in the effluent, indicating that the acetylated form of vitamin E is cleaved by brush border enzymes in the small intestine. CONCLUSIONS: This study shows that even in the absence of digestive enzymes and bile salts, the appropriately solubilized acetylated form of α-tocopherol exhibits the same bioavailability as free α-tocopherol. This suggests that both forms can be absorbed equally under maldigestion conditions such as present clinically during enteral tube feeding.

Acute experimental stress evokes a differential gender-determined increase in human intestinal macromolecular permeability.

BACKGROUND: Intestinal epithelial dysfunction is a common pathophysiologic feature in irritable bowel syndrome (IBS) patients and might be the link to its clinical manifestations. We previously showed that chronic psychosocial stress induces jejunal epithelial barrier dysfunction; however, whether this epithelial response is gender-specific and might thus explain the enhanced female susceptibility to IBS remains unknown. METHODS: Intestinal responses to acute stress were compared in age-matched groups of healthy women and men (n = 10 each) experiencing low background stress. A 20-cm jejunal segment, was perfused with an isosmotic solution, and intestinal effluents were collected under basal conditions, for 15 min during cold pain stress and for a 45-min recovery period. Epithelial function (net water flux and albumin output), changes in stress hormones, and cardiovascular and psychologic responses to cold stress were measured. KEY RESULTS: Heart rate and blood pressure significantly increased during cold pain stress with no differences between men and women. Adrenocorticotropic hormone and cortisol levels during cold pain stress were significantly higher in men. Basal net water flux and epithelial permeability were similar in men and women. Cold pain stress increased water flux in both groups (72 ± 23 and 107 ± 18 µL min(-1) cm(-1) , respectively; F(5, 90) = 5.5; P = 0.003 for Time) and, interestingly, this was associated with a marked increase of albumin permeability in women but not in men (0.8 ± 0.2 vs.-0.7 ± 0.2 mg/15 min; P < 0.0001). CONCLUSIONS & INFERENCES: Intestinal macromolecular permeability in response to acute experimental stress is increased in healthy women, a mechanism that may contribute to female oversusceptibility to IBS.

Variability of Bartonella genotypes among small mammals in Spain.

In order to study which Bartonella genotypes are circulating among small mammals in Spain, we analyzed the spleens of 395 animals from three different areas-247 animals from the Basque Country (northern Spain), 121 animals from Catalonia (northeastern Spain), and 27 animals from Madrid (central Spain)-by a triplex PCR combined with a reverse line blot previously described by our group. The prevalence of Bartonella was 26.8% (106/395), and in 4.8% (19/395) of the animals more than one Bartonella genotype was detected. The study of gltA and the intergenic transcribed spacer in the positive samples demonstrated a large diversity, allowing the assignation of them into 22 genotypes. The most prevalent genotypes were 2 and 3, which are closely related to Bartonella taylorii. In addition, nine genotypes were associated with specific mammal species. Genotypes close to the zoonotic Bartonella grahamii, Bartonella elizabethae, and Bartonella rochalimae were also detected. Ten genotypes showed a percentage of similarity with known Bartonella species lower than 96%, suggesting the presence of potential new species. Further studies of the impact of these pathogens on human health and especially in cases of febrile illness in Spain are strongly recommended. Furthermore, our method has been updated with 21 new probes in a final panel of 36, which represents a robust molecular tool for clinical and environmental Bartonella studies.

Impaired intestinal gas propulsion in manometrically proven dysmotility and in irritable bowel syndrome.

BACKGROUND: Intestinal manometry is the current gold standard for diagnosing small bowel dysmotility; however, the functional significance of abnormal manometry is unknown. Our aim was to determine whether, and to what extent, intestinal gas propulsion is impaired in patients with manometrically proven dysmotility compared with healthy controls and patients with IBS. METHODS: Clearance and tolerance of a jejunal gas load (12 mL min(-1) for 2 h) were measured in 15 patients with severe abdominal symptoms and intestinal dysmotility evidenced by manometry, 15 patients with IBS and 15 healthy subjects. Thereafter, the effect of neostigmine (0.5 mg i.v. bolus) vs placebo (i.v. saline) was tested in six dysmotility patients. KEY RESULTS: After 2-h gas infusion, patients with dysmotility developed significantly more gas retention (717 +/- 91 mL) than IBS patients (372 +/- 82 mL; P = 0.0037) and healthy subjects (17 +/- 67 mL; P < 0.0001 vs dysmotility; P = 0.0060 vs IBS). Despite the greater retention in dysmotility patients, abdominal perception (2.5 +/- 0.6 score) and distension (7 +/- 2 mm girth increment) were similar to IBS (3.9 +/- 0.6 score and 7 +/- 2 mm, respectively). In dysmotility patients, neostigmine produced immediate clearance of gas, and by 30 min had reduced gas retention (by -552 +/- 182 vs 72 +/- 58 mL after saline; P = 0.008), abdominal symptoms (by -0.8 +/- 0.3 score vs 0.3 +/- 0.2 after saline; P = 0.019) and distension (girth change -5 +/- 1 mm; P = 0.003 vs-2 +/- 2 mm after saline). CONCLUSION & INFERENCES: Patients with manometric dysmotility have markedly impaired intestinal gas propulsion. In IBS patients, impaired gas propulsion is less pronounced but associated with concomitant sensory dysfunction and poor tolerance of gas retention.

Alunos do ensino médio e atratividade da carreira docente no Brasil / Secondary school students and the attractiveness of a teaching career in Brazil

O artigo traz os resultados de pesquisa cujo objetivo foi investigar a atratividade da carreira docente no Brasil pela ótica de alunos concluintes do ensino médio, uma vez que se tem divulgado a perda de interesse pela opção profissional pelo magsitério por parte dos adolescentes. O estudo foi realizado em escolas públicas e particulares de cidades de grande ou médio porte das diferentes regiões do país. Os dados utilizados para as análises têm origem em duas fontes: questionário e grupos de discussão. Nos resultados, a rejeição à carreira docente é recorrente entre os jovens pesquisados. As justificativas dos estudantes para a falta de atratividade da carreira se relacionam à ausência de identificação pessoal com a docência, às condições sociais e financeiras de exercício da profissão, à própria experiência escolar dos alunos e à influência familiar.(AU)

The article presents the results of research, the objective of which was to investigate the attractiveness of a teaching career in Brazil from the viewpoint of students in the final year of secondary education, since it has been widely disclosed that there is a loss of interest in choosing teaching as a profession on the part of adolescents. The study was carried out in public and private schools in large or medium-size cities in different regions in Brazil. The data used for the analyses originated from two sources: a questionnaire and discussion groups. The results show that rejection of a teaching career is a recurrent theme among the young people involved in the research. The justifications of the students for the lack of attractiveness of the career are related to the absence of a personal identification with teaching, the social and financial conditions associated with exercising the profession, the students' own school experience and family influence.(AU)

Micropolítica escolar e estratégias para o desenvolvimento do protagonismo juvenil / School Micropolicy and youth protagonism development strategies

Este artigo aborda a construção do protagonismo juvenil no âmbito da reforma do ensino médio, discutindo resultados parciais de pesquisa mais ampla, os quais focalizaram cinco escolas em dois estados brasileiros. O objetivo geral da investigação foi verificar como as escolas interagiam com as diretrizes oficiais que propõem a participação efetiva de alunos e dos pais na dinâmica escolar e quais são as mediações que articulam os microprocessos institucionais às orientações políticas e sociais mais abrangentes. Este texto, no entanto, analisa apenas o espaço que o pretendido desenvolvimento do protagonismo juvenil ocupa na trama da micropolitica escolar e, para isso, vale-se de conceitos de Stephen J. Ball como tentativa de 'ler' a intrincada rede de relações intramuros que ressignifica as prescrições de orgãos centrais(AU)

Usefulness of jejunal biopsy in the study of intestinal malabsorption in the elderly.

BACKGROUND: small bowel structure and function are not different between elderly people and young people. Thus, in principle it is advisable to perform diagnostic investigation of elderly patients as well as younger patients when they present with symptoms suggestive of intestinal malabsorption. A key test for the etiologic diagnosis of intestinal malabsorption, jejunal biopsy, has not been specifically examined to assess its usefulness and risk of complications in this advanced age patients. AIM: to establish the usefulness of jejunal biopsy with the Watson's capsule in the elderly patients with suspected intestinal malabsorption. PATIENTS: patients older than 65 years referred to our Unit for performance of a jejunal biopsy from 1996 to 2001 for suspicion of intestinal malabsorption. RESULTS: forty-seven patients were included. Appropriate biopsy sample was obtained in 45 cases, although in 3 patients a second try was required. Histologic findings: partial villous atrophy in 10 cases (22.2%), complete villous atrophy in 5 cases (11.1%), intraepithelial lymphocytosis in 5 cases (11.1%), and single cases of intestinal lymphangiectasia, amyloidosis, unspecific jejunitis, and Whipple's disease. Histology was normal in 19 cases (42%). Definitive diagnosis was celiac disease in 14 patients, bacterial overgrowth in 3, jejunitis in 3, Whipple's disease in 1, lymphangiectasia in 1, atrophic gastritis in 3, amyloidosis in 1, and ischemic colitis in 1. Jejunal biopsy achieved an etiologic diagnosis in 20 patients. There were no cases of perforations or bleeding. CONCLUSION: jejunal biopsy is a useful and safe test for the etiologic diagnosis of intestinal malabsorption in elderly patients.

Protagonismo juvenil na literatura especializada e na reforma do ensino médio / Juvenile protagonism in specialized literature and in secondary-school education reform

O 'protagonismo juvenil' tem tido ampla repercussão na área educacional, principalmente a partir da implementação da reforma curricular do ensino médio, cujas diretrizes adotam esse conceito como um dos pilares das inovações sugeridas. No entanto, o tema é sujeito a diferentes interpretações. Com a preocupação de maior precisão conceitual, este artigo recorre às definições de diversos autores como contraponto para a análise do protagonismo tal como proposto pelo documento oficial da reforma(AU)

Linfoma de Hodgkin con afectación ósea: comunicación de un caso y revisión de la literatura / Bone primary Hodgkin´s lymphoma: report of a case and review of the literature

Existen pocas comunicaciones en la literatura acerca de la afectación ósea primaria por linfoma de Hodgkin. El linfoma de Hodgkin representa menos del 0'15 por ciento de los tumores malignos primarios del hueso, aunque por radiología es frecuente detectar lesiones óseas en pacientes con enfermedad de Hodgkin. Comunicamos el caso de un paciente inicialmente diagnosticado de linfoma de Hodgkin en fémur izquierdo, tratado con un régimen combinado de quimioradioterapia secuencial, que permanece libre de recaída a cuatro años después, aprovechando para revisar la literatura respecto a su diagnóstico y tratamiento (AU)

Escola e fábrica: vozes de trabalhadores em uma indústria de ponta / School and factory in the voice of workers from a cutting-edge industry

O objetivo deste artigo é o de apresentar parte dos resultados de ampla pesquisa, na qual se estudou a qualificação como construção social, privilegiando-se dois campos de análise: a escola e a fábrica. A pesquisa focalizou uma escola pública, duas unidades do Senai e uma indústria metal-mecânica, localizada no interior do Estado de São Paulo. Neste artigo, discutem-se alguns dados obtidos no âmbito da fábrica, com destaque para o olhar dos trabalhadores sobre o valor da escolarização, não só para o exercício da profissão, mas para a vida social e familiar. Os procedimentos adotados pela indústria, visando à qualificação profissional e à adesão dos trabalhadores aos objetivos empresariais, são também muito bem aceitos. A análise dos dados permitiu, todavia, desvelar conflitos, contradições e idealizações que os discursos consensuais não conseguem de todo ocultar(AU)

[Reference values for lead in blood in urban population in southern Brazil]. / Valores de referência para plumbemia em uma população urbana do Sul do Brasil.

OBJECTIVE: To describe the reference values for lead in blood in an urban population in the city of Londrina, in the state of Paraná, Brazil. MATERIALS AND METHODS: The reference population was composed of 520 adult volunteers who were assessed from November 1994 to December 1996. Exclusion criteria were: occupational exposure to lead, exposure through personal habits or practices, smoking more than 10 cigarettes per day, and living near industrial plants or other places that use lead in their production processes. Also excluded were individuals with abnormal clinical or laboratory results or with chronic diseases or cardiovascular disorders. Lead blood levels were determined using air-acetylene flame atomic absorption spectrophotometry. The detectable limit was 1.23 micrograms/dL. After the analyses of lead in blood, the following values were determined: minimum value, first quartile, median, third quartile, and maximum value; geometric mean; 95% confidence interval; experimental interval; and reference value. RESULTS: The reference values for lead in blood ranged from 1.20 micrograms/dL to 13.72 micrograms/dL. The geometric mean was 5.5 micrograms/dL. CONCLUSIONS: In general, the values found in this study are lower than those that have been reported for other countries. Additional data should be gathered from Brazilian populations living in more-industrialized areas.

Isothermal titration calorimetric analysis of the interaction between cationic lipids and plasmid DNA.

The effects of buffer and ionic strength upon the enthalpy of binding between plasmid DNA and a variety of cationic lipids used to enhance cellular transfection were studied using isothermal titration calorimetry at 25.0 degrees C and pH 7.4. The cationic lipids DOTAP (1,2-dioleoyl-3-trimethyl ammonium propane), DDAB (dimethyl dioctadecyl ammonium bromide), DOTAP:cholesterol (1:1), and DDAB:cholesterol (1:1) bound endothermally to plasmid DNA with a negligible proton exchange with buffer. In contrast, DOTAP: DOPE (L-alpha-dioleoyl phosphatidyl ethanolamine) (1:1) and DDAB:DOPE (1:1) liposomes displayed a negative enthalpy and a significant uptake of protons upon binding to plasmid DNA at neutral pH. These findings are most easily explained by a change in the apparent pKa of the amino group of DOPE upon binding. Complexes formed by reverse addition methods (DNA into lipid) produced different thermograms, sizes, zeta potentials, and aggregation behavior, suggesting that structurally different complexes were formed in each titration direction. Titrations performed in both directions in the presence of increasing ionic strength revealed a progressive decrease in the heat of binding and an increase in the lipid to DNA charge ratio at which aggregation occurred. The unfavorable binding enthalpy for the cationic lipids alone and with cholesterol implies an entropy-driven interaction, while the negative enthalpies observed with DOPE-containing lipid mixtures suggest an additional contribution from changes in protonation of DOPE.

Characterization of cationic vector-based gene delivery vehicles using isothermal titration and differential scanning calorimetry.

Within the past 10 years, major advances in the design and development of differential scanning calorimeters (DSC) (1) and isothermal titration calorimeters (ITC) (2) have resulted in an unparalleled level of sensitivity, stability, and reproducibility in calorimetric measurements of large molecules. These improvements have allowed the thermal stability and ligand binding processes of biological macromolecules to be thermodynamically characterized with speed, accuracy, and convenience. With their increasing commercial availability, experiments that were previously limited to specialist calorimetry laboratories can now be routinely performed by most investigators.