Photoswitching/back-switching assessment of biobased cellulose acetate/azobenzene handleable films under visible-light LED irradiation.

The light-induced processes performed by photofunctional polymer films are crucial aspects of developing integrated energy storage devices properly. Herein, we report the preparation, characterization, and study of the optical properties of a series of biobased cellulose acetate/azobenzene (CA/Az1) handleable films at different compositions. The photoswitching/back-switching behavior of the samples was investigated using varied LED irradiation sources. Additionally, poly(ethylene glycol) (PEG) was deposited onto cellulose acetate/azobenzene films to study the back-switching process's effect and nature in the fabricated films. Interestingly, the melting enthalpies of PEG before and after being irradiated with blue LED light were 2.5 mJ and 0.8 mJ, respectively. Conveniently, FTIR and UV-visible spectroscopy, thermogravimetry (TGA), contact angle, differential scanning calorimetry (DSC), polarized light microscopy (PLM), and atomic force microscopy (AFM) were used for the characterization of the sample films. Complementarily, theoretical electronic calculations provided a consistent approach to the energetic change in the dihedral angles and non-covalent interaction for the trans and cis isomer in the presence of cellulose acetate monomer. The results of this study revealed that CA/Az1 films are viable photoactive materials displaying handleability attributes with potential uses in harvesting, converting, and storing light energy.

A facile approach for tuning optical and surface properties of novel biobased Alginate/POTE handleable films via solvent vapor exposure.

Novel biobased films consisting of alginate blends with poly (octanoic acid 2-thiophen-3-yl-ethyl ester) (POTE), a conducting polymer, were prepared by solution casting, and their optical, morphological, thermal, and surface properties were studied. Using UV-visible spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the effects of tetrahydrofuran solvent vapors on the optical properties and surface morphology of biobased films with different POTE contents were studied. Results indicate that morphological rearrangements of POTE take place during the process of solvent exposure. Specifically, the solvent vapor induced the formation of POTE small crystalline domains, which allows envisioning the potential of tuning UV-visible absorbance and wettability behavior of biobased films. Finally, theoretical electronic calculations (specifically frontier molecular orbitals analysis) provided consistent evidence on POTE's preferential orientation and selectivity toward the THF-vapor medium.

Optical, morphological and photocatalytic properties of biobased tractable films of chitosan/donor-acceptor polymer blends.

Biobased tractable films consisting of blends of chitosan (CS) with polymer bearing carbazole derivatives as pendant groups and fluorene-thiophene as donor-acceptor units (referred to as DA) were prepared, and their optical, morphological and photocatalytic properties were studied. DA was dissolved in tetrahydrofuran (THF) and mixed with an acidified aqueous solution containing chitosan to obtain chitosan/DA (CS/DA) films by solution casting. The fabricated biobased films were characterized using spectroscopic techniques (FT-IR and UV-vis), thermogravimetry, mechanical assays, contact angle analysis, and atomic force microscopy (AFM). The effects of varying DA compositions and the results of exposure to visible-light irradiation of the films were also analyzed. The results indicated the existence of interactions between chitosan and DA and a potentially profitable light-driven response of these biobased films. This behavior was reflected in the optical, topographical, and contact angle properties of the films, which exhibited different characteristics before and after visible-light exposure. Finally, the photocatalytic performance of the biobased films was tested via the decomposition of methyl orange (MO), as a reaction model system. Our results revealed a significant photocatalytic activity (according to biobased film composition, approximately 64 % and 87 % of methyl orange were degraded under continuous visible-light irradiation for 120 min) of the films which is attributed to the combined presence and synergetic effects of the film-forming ability of chitosan and the photoproperties of DA.

Efecto antiangiogénico del ácido cafeico y pinocembrina en el proceso de angiogénesis fisiológica de fetos de pollo / Anti-angiogenic effect of caffeic acid and pinocembrin in the process of physiological angiogenesis of chicken fetuses

La angiogénesis es el proceso por el cual se forman nuevos vasos sanguíneos a partir de otros ya existentes. Para que esto se lleve a cabo de forma correcta debe existir un balance entre los factores proangiogénicos y los factores antiangiogénicos dentro del microambiente tisular. Por otra parte, la existencia de productos químicos naturales como los polifenoles, que son capaces de adquirirse en la dieta, inducen a estos factores a intervenir en el proceso de angiogénesis. Se administraron los polifenoles en filtros de metilcelulosa sobre la membrana alantocoriónica de huevos White Leghorn, manteniendo el posterior desarrollo normal del feto. Se utilizaron 15 fetos de pollo fijados en formalina tamponada, a los cuales se extrajo el corazón. El procesamiento de las muestras de corazón se realizó a través de técnicas histológicas, histoquímicas e inmunohistoquímica. Finalmente se evaluó la presencia del VEGF y la capacidad de formar vasos sanguíneos bajo el tratamiento con los polifenoles. La inmunorreactividad fue cuantificada mediante Image J®. Los resultados indican que Ácido cafeico y Pinocembrina disminuyen la densidad microvascular y la expresión de VEGF en corazones de fetos de pollo tratados con estos polifenoles. Tanto el Ácido Cafeico como la Pinocembrina cumplen un rol inhibitorio en el proceso de angiogénesis fisiológica en corazón de pollo, pudiendo modular las vías de señalización mediadas por los VEGFR o modulando la disponibilidad de VEGF. Estos polifenoles podrían utilizarse para el estudio de otros tejidos asociados a angiogénesis patológica.

Angiogenesis is the process by which new blood vessels are formed from other existing ones. A balance between proangiogenic factors and anti-angiogenic factors within the microenvironment must exist for the process to be carried out correctly. Similarly, the existence of natural chemicals such as polyphenols, which are capable of being acquired in the diet, induce these factors in the angiogenic process. Polyphenols were administered in the methylcellulose filters on the of chorioallantoic membrane of White Leghorn eggs, maintaining the normal posterior development of the fetus. 15 chicken fetuses were fixed in buffered formalin, obtaining the hearts to histological processing, performing histological, histochemical and immunohistochemical techniques. VEGF levels and the ability of the blood vessels growing under the stimulation of the polyphenols were evaluated. Immunoreactivity was quantified by Image J. The results indicate that caffeic acid and pinocembrin decreased microvascular density and VEGF expression in hearts stimulated with these polyphenols. Both the caffeic and pinocembrin acids play an inhibitory role in the physiological angiogenesis process in the chicken heart, which decrease the microvascular density and could act by modulating the signaling pathways mediated by the VEGFR or by modulating the availability of VEGF. The use of these polyphenols could be useful in studies of other tissues associated with pathological angiogenesis.

Análisis de expresión de calreticulina en vena safena parva / Calreticulin expression analysis in small saphenous vein

La proteína chaperona Calreticulina (CRT), ha sido identificada en retículo endoplásmico (RE) y últimamente en la matriz extracelular (MEC) de predentina y arterias, atribuyéndole diferentes funciones extracelulares entre las que destacan la adhesión celular, regulación de la MEC y prevención en la formación de trombos. El objetivo del estudio fue identificar la presencia de CRT en MEC de vena safena parva. Se extrajo una muestra de vena safena parva de un espécimen masculino y luego fue procesada por medios histológicos e inmunohistoquímicos para identificar su presencia. Mediante técnicas de inmunohistoquímica se pudo evidenciar la presencia de CRT en la MEC de la adventicia de vena safena parva. La presencia de CRT en MEC de safena parva orienta a que CRT tienen funciones de tipo extracelular en esta localización, pero es necesario realizar estudios más precisos para dilucidar sus principales funciones en la zona.

Calreticulin (CRT) protein, has been identified in the endoplasmic reticulum (ER) and lately in the extracellular matrix (ECM) of predentine and arteries. It is responsible for different extracellular functions, such as cell adhesion, ECM regulation, and the prevention of thrombosis. The aim was to identify the presence of CRT in ECM of small saphenous vein. A sample of small saphenous vein from a male specimen was extracted and then processed by histological and immunohistochemical assays to identify its presence. The presence of CRT in the ECM of the small saphenous vein was observed by immunohistochemical techniques. The presence of CRT in the small saphenous vein ECM, indicates that CRT have extracellular functions in this area, however, more precise studies are necessary to determine its main functions.

Association between adiposity levels and cognitive impairment in the Chilean older adult population.

Although both obesity and ageing are risk factors for cognitive impairment, there is no evidence in Chile on how obesity levels are associated with cognitive function. Therefore, the aim of the present study was to investigate the association between adiposity levels and cognitive impairment in older Chilean adults. This cross-sectional study includes 1384 participants, over 60 years of age, from the Chilean National Health Survey 2009-2010. Cognitive impairment was evaluated using the Mini-Mental State Examination. BMI and waist circumference (WC) were used as measures of adiposity. Compared with people with a normal BMI, the odds of cognitive impairment were higher in participants who were underweight (OR 4·44; 95 % CI 2·43, 6·45; P < 0·0001), overweight (OR 1·86; 95 % CI 1·06, 2·66; P = 0·031) and obese (OR 2·26; 95 % CI 1·31, 3·21; P = 0·003). The associations were robust after adjustment for confounding variables. Similar results were observed for WC. Low and high levels of adiposity are associated with an increased likelihood of cognitive impairment in older adults in Chile.

Amino Acid-Functionalized Polyelectrolyte Films as Bioactive Surfaces for Cell Adhesion.

Surfaces were prepared with polyelectrolyte derivatives of poly(styrene- alt-maleic anhydride) (PSMA) functionalized with amino acids of different hydropathy indices, with the aim of evaluating the effect of the chemical functionality of polyelectrolytes on SH-SY5Y neuroblastoma cell adhesion. Functionalizing PSMA derivatives with l-glutamine, l-methionine, and l-tyrosine yielded PSMA-Gln, PSMA-Met, and PSMA-Tyr polyelectrolytes, respectively. We first studied the adsorption behavior of PSMA functionalized with amino acids on silicon wafer surfaces modified with 3-aminopropyltriethoxysilane at pH 4.0 and 7.0 and at low and high ionic strengths. The highest rate of polyelectrolyte adsorption was at pH 4.0 and high ionic strength and was higher with the glutamine and tyrosine films. The advance contact angles (θA) of the polyelectrolyte surfaces showed a moderate effect of ionic strength and pH on polyelectrolyte film wettability, with PSMA-Tyr being slightly more hydrophobic. Atomic force microscopy images of the polyelectrolyte surfaces showed two types of morphology: the well-defined globular nanostructure of PSMA-Met and PSMA-Tyr and densely packed nanofibrous-like structure of PSMA-Gln. The highest level of ionic strength caused a slight decrease in the size of the nanostructure that formed the surface domains, which was reflected in the degree of surface roughness. Cell adhesion assays with the polyelectrolyte film showed that SH-SY5Y neuroblastoma cells cultured on PSMA-Met present a well-extended morphology characterized by a stellate shape, with five or more actin-rich thin processes, whereas SH-SY5Y cells that were seeded on PSMA-Gln and PSMA-Tyr have a round morphology, with fewer and shorter processes. These results indicate that it is possible to modulate the surface characteristics of polyelectrolyte films based on their chemical functionality and environmental parameters such as pH and ionic strength in order to evaluate their effect on cell adhesion. Thus, surfaces prepared from polyelectrolytes functionalized with amino acids are an attractive and simple platform for cell adhesion, which can be used in developing biomaterials with modulated surface properties.

Characterization of the animal by-product meal industry in Costa Rica: Manufacturing practices through the production chain and food safety.

Animal by-product rendering establishments are still relevant industries worldwide. Animal by-product meal safety is paramount to protect feed, animals, and the rest of the food chain from unwanted contamination. As microbiological contamination may arise from inadequate processing of slaughterhouse waste and deficiencies in good manufacturing practices within the rendering facilities, we conducted an overall establishment's inspection, including the product in several parts of the process.An evaluation of the Good Manufacturing Practices (GMP) was carried out, which included the location and access (i.e., admission) to the facilities, integrated pest management programs, physical condition of the facilities (e.g., infrastructure), equipments, vehicles and transportation, as well as critical control points (i.e., particle size and temperature set at 50 mm, 133°C at atmospheric pressure for 20 min, respectively) recommended by the OIE and the European Commission. The most sensitive points according to the evaluation are physical structure of the facilities (avg 42.2%), access to the facilities (avg 48.6%), and cleaning procedures (avg 51.4%).Also, indicator microorganisms (Salmonella spp., Clostridium spp., total coliforms, E. coli, E. coli O157:H7) were used to evaluate the safety in different parts of the animal meal production process. There was a prevalence of Salmonella spp. of 12.9, 14.3, and 33.3% in Meat and Bone Meal (MBM), poultry by-products, and fish meal, respectively. However, there were no significant differences (P = 0.73) in the prevalence between the different animal meals, according to the data collected.It was also observed that renderings associated with the poultry industry (i.e., 92.0%) obtained the best ratings overall, which reflects a satisfactory development of this sector and the integration of its production system as a whole.

Modulation of intracellular pH in human ovarian cancer.

To sustain tumor growth, the cancer cells need to adapt to low levels of oxygen (i.e., hypoxia) in the tumor tissue and to the tumor-associated acidic microenvironment. In this phenomenon, the activation of the sodium/proton exchanger 1 (NHE1) at the plasma membrane and the hypoxia-inducible factor (HIF) are critical for the control of the intracellular pH (pHi) and for hypoxia adaptation, respectively. Interestingly, both of these mechanisms end in sustaining cancer cell proliferation. However, regulatory mechanisms of pHi in human ovary tissue and in malignant ascites are unknown. Additionally, a potential role of NHE1 in the modulation of H(+) efflux in human ovarian cancer cells is unknown. In this review, we discussed the characteristics of tumor microenvironment of primary human ovarian tumors and tumor ascites, in terms of pHi regulatory mechanisms and oxygen level. The findings described in the literature suggest that NHE1 may likely play a role in pHi regulation and cell proliferation in human ovarian cancer, potentially involving HIF2α activation. Since ovarian cancer is the fifth cause of prevalence of women cancer in Chile and is usually of late diagnosis, i.e., when the disease jeopardizes peritoneal cavity and other organs, resulting in reduced patient survival, new efforts are required to improve patient-life span and for a better understanding of the pathophysiology of the disease. The potential advantage of the use of amiloride and amiloride-derivatives for cancer treatment in terms of NHE1 expression and activity is also discussed as a therapeutic approach in human ovarian cancer.

Insulin receptor isoforms: an integrated view focused on gestational diabetes mellitus.

The human insulin receptor (IR) exists in two isoforms that differ by the absence (IR-A) or the presence (IR-B) of a 12-amino acid segment encoded by exon 11. Both isoforms are functionally distinct regarding their binding affinities and intracellular signalling. However, the underlying mechanisms related to their cellular functions in several tissues are only partially understood. In this review, we summarize the current knowledge in this field regarding the alternative splicing of IR isoform, tissue-specific distribution and signalling both in physiology and disease, with an emphasis on the human placenta in gestational diabetes mellitus (GDM). Furthermore, we discuss the clinical relevance of IR isoforms highlighted by findings that show altered insulin signalling due to differential IR-A and IR-B expression in human placental endothelium in GDM pregnancies. Future research and clinical studies focused on the role of IR isoform signalling might provide novel therapeutic targets for treating GDM to improve the adverse maternal and neonatal outcomes.

Human supraphysiological gestational weight gain and fetoplacental vascular dysfunction.

OBJECTIVE: Human foetal development and growth in an environment of maternal obesity associates with high risk of cardiovascular disease and adverse neonatal outcome. We studied whether supraphysiological gestational weight gain results in human fetoplacental endothelial dysfunction and altered fetoplacental vascular reactivity. METHODS: Primary cultures of human umbilical vein endothelial cells (HUVECs) and umbilical vein rings were obtained from pregnant women (112 total of patients recruited, 7 patients dropped out) exhibiting prepregnancy normal weight that ended with a physiological (pGWG (n=67), total weight gain 11.5-16 kg, rates of weight gain ≤0.42 kg per week) or supraphysiological (spGWG (n=38), total weight gain >16 kg, rates of weight gain >0.42 kg per week) gestational weight gain (reference values from US Institute of Medicine guidelines). Vascular reactivity to insulin (0.1-1000 nmol l(-1), 5 min) in KCl-preconstricted vein rings was measured using a wire myograph. Protein levels of human equilibrative nucleoside transporter 1 (hENT1), total and Ser(1177)- or Thr(495)-phosphorylated endothelial nitric oxide synthase (eNOS) were detected by western blot or immunofluorescence, and adenosine transport (0-250 µmol l(-1) adenosine, 2 µCi ml(-1) [(3)H]adenosine, 20 s, 25 °C) was measured in the presence or absence of 1 µmol l(-1) nitrobenzylthioinosine (hENT1 inhibitor) or 10 µmol l(-1) chlorpromazine (CPZ, endocytosis inhibitor) in HUVECs. RESULTS: spGWG associates with reduced NOS activity-dependent dilation of vein rings (P=0.001), lower eNOS expression and higher Thr(495) (P=0.044), but unaltered Ser(1177)eNOS phosphorylation. hENT1-adenosine maximal transport activity was reduced (P=0.041), but the expression was increased (P=0.001) in HUVECs from this group. CPZ increased hENT1-adenosine transport (P=0.040) and hENT1 plasma membrane accumulation only in cells from pGWG. CONCLUSION: spGWG in women with a normal prepregnancy weight causes lower fetoplacental vascular reactivity owing to the downregulation of eNOS activity and adenosine transport in HUVECs. Maternal spGWG is a detrimental condition for human fetoplacental endothelial function and reducing these alterations could result in a better neonate outcome.

Insulin restores L-arginine transport requiring adenosine receptors activation in umbilical vein endothelium from late-onset preeclampsia.

INTRODUCTION: Preeclampsia is associated with impaired placental vasodilation and reduced endothelial nitric oxide synthase (eNOS) activity in the foetoplacental circulation. Adenosine and insulin stimulate vasodilation in endothelial cells, and this activity is mediated by adenosine receptor activation in uncomplicated pregnancies; however, this activity has yet to be examined in preeclampsia. Early onset preeclampsia is associated with severe placental vasculature alterations that lead to altered foetus growth and development, but whether late-onset preeclampsia (LOPE) alters foetoplacental vascular function is unknown. METHODS: Vascular reactivity to insulin (0.1-1000 nmol/L, 5 min) and adenosine (1 mmol/L, 5 min) was measured in KCl-preconstricted human umbilical vein rings from normal and LOPE pregnancies using a wire myograph. The protein levels of human cationic amino acid transporter 1 (hCAT-1), adenosine receptor subtypes, total and Ser¹¹77- or Thr495-phosphorylated eNOS were detected via Western blot, and L-arginine transport (0-1000 µmol/L L-arginine, 3 µCi/mL L-[³H]arginine, 20 s, 37 °C) was measured in the presence or absence of insulin and adenosine receptor agonists or antagonists in human umbilical vein endothelial cells (HUVECs) from normal and LOPE pregnancies. RESULTS: LOPE increased the maximal L-arginine transport capacity and hCAT-1 and eNOS expression and activity compared with normal conditions. The A(2A) adenosine receptor (A(2A)AR) antagonist ZM-241385 blocked these effects of LOPE. Insulin-mediated umbilical vein ring relaxation was lower in LOPE pregnancies than in normal pregnancies and was restored using the A(2A)AR antagonist. DISCUSSION AND CONCLUSIONS: The reduced foetoplacental vascular response to insulin may result from A(2A)AR activation in LOPE pregnancies.

[Could infant euthanasia be ever acceptable?]. / ¿Podría ser aceptable la eutanasia infantil?

The recent enactment of a law that allows infant euthanasia in Belgium raises questions with varied answers. To contribute to a better understanding of the topic, euthanasia and legislation concepts are described. After a bioethical analysis, we propose as conclusion that children euthanasia could only be acceptable in very exceptional situations in which palliative measures have failed. The answer should be that it is not acceptable in our setting, not until we have public policies, protocols and palliative care services for terminally ill children.

Follicular dynamics, interval to ovulation and fertility after AI in short-term progesterone and PGF2α oestrous synchronization protocol in sheep.

The study was aimed to assess the influence that short-term progesterone treatments have on follicular dynamics, oestrus and ovulation in sheep. The treatment was tested thereafter in a field trial to assess its fertility after AI with fresh semen. In a first experiment, 12 ewes without CL were grouped to receive a new (n = 6) or used CIDR (n = 6) for 7 days and blood samples were obtained to follow plasma progesterone profiles. In a second experiment, 39 cycling ewes were synchronized by a 7-day P4+PGF2α protocol using a new (n = 20) or a 7-day used CIDR (n = 19). Half of both groups received 400 IU eCG and half remained untreated as controls. Ultrasound ovarian examination and oestrous detection were used to compare follicular dynamics, oestrus and ovulation in both groups. In a third experiment, 288 ewes in 3 farms were synchronized by the short-term P4+PGF2α+eCG protocol and ewes were AI with fresh semen 24 h after oestrous detection. Lambing performance was used to test the fertility of the treatment. In Experiment 1, ewes with new inserts presented higher P4 concentration than ewes with used inserts throughout the sampling period (p < 0.05) and exhibited a P4 peak at days 1-2 of the treatment that was not observed in ewes with used inserts. In Experiment 2, ewes treated with new and used inserts show similar ovarian and behavioral traits (p > 0.10). However, ewes treated with eCG show shorter interval to oestrus (p = 0.004) and tend to have larger mature CL (p = 0.06). In Experiment 3, oestrous presentation and lambing performance after AI with fresh semen was considered normal compared to published results. Results suggest that the oestrous synchronization protocol based on P4+PGF2α allows little control of follicular dynamics without compromising fertility after AI with fresh semen provided that eCG is added at the end of the treatment.

Review: Differential placental macrovascular and microvascular endothelial dysfunction in gestational diabetes.

Human endothelial dysfunction is a common feature in many diseases of pregnancy, such as gestational diabetes (GD). Metabolic changes include abnormal synthesis of nitric oxide (NO) and abnormal membrane transport of l-arginine and adenosine in primary cultures of human umbilical vein (HUVEC, macrovascular) and placental microvillus (hPMEC, microvascular) endothelial cells. These alterations are associated with modifications in the expression and activity of endothelial (eNOS) and inducible (iNOS) NO synthases, respectively, an effect that is maintained at least up to passage 5 in culture. HUVEC and hPMEC exhibit expression and activity of the human cationic amino acid transporter 1 (hCAT-1), equilibrative nucleoside transporters 1 (hENT1) and hENT2, as well as the corresponding SLC7A1, SLC29A1 and SLC29A2 gene promoter activities. Altered gene expression results from increased NO level, protein kinase C, mitogen-activated protein kinases, and hCHOP-C/EBPα transcription factor activation. Reduced ENT-mediated adenosine transport in GD is associated with stimulation of the l-arginine/NO pathway, and mainly due to reduced expression and activity of hENT1. In addition, hENT2 activity seems able to restore the reduced adenosine transport in GD. Additionally, insulin exerts a differential modulation of endothelial cells from macrocirculation compared with microcirculation, possibly due to expression of different insulin receptor isoforms. It is suggested that a common functional characteristic leading to changes in the bioavailability of adenosine and metabolism of l-arginine is evidenced by human fetal micro and macrovascular endothelium in GD.

Supuración crónica perianal por cuerpo extraño / Chronic perianal discharge caused by a foreign body

El empalamiento perineal es una lesión poco frecuente, que puede dar origen a un cuadro de supuración crónica perineal cuya etiología no es el habitual absceso o fístula perianal. Se presenta el caso de un paciente de 34 años que sufrió un empalamiento perineal en accidente laboral, presentando descarga purulenta perianal en forma casi permanente por cinco años. Durante su evolución se trató como una fístula, con fistulectomía parcial y ligadura elástica, sin remisión de la sintomatología. Se realizó fistulografía bajo TAC y colonoscopía con inyección de azul de metileno y agua oxigenada por el trayecto fistuloso, que no evidenciaron comunicación a recto, por lo que se decidió la exploración quirúrgica. Se extrajo un cuerpo extraño, correspondiente a tela, luego de lo cual se objetivó la cicatrización del orificio fistuloso a las dos semanas. El último control se realizó al mes de la cirugía.

Poly(tetrahydropyranyl-2-methyl methacrylate): comparative study in solution and at the air/water interface.

In this work a comparative study of different molecular-weight fractions of the amphiphilic polymer poly(tetrahydropyranyl-2-methyl methacrylate) (PTHPMM) in solution and at the air/water interface is reported. The synthesis of the polymer was carried out in solution by radical polymerization. The polymer was fractionated and five fractions were studied in solution and at the air/water interface. The weight-average molecular weight M(w), the second virial coefficient A(2), and the radius of gyration R(g) were determined in toluene by static light scattering. Intrinsic viscosities [eta] of the polymer fractions in three solvents were obtained. The Kuhn-Mark-Houwink-Sakurada relationships were established. The Langmuir isotherms for different polymer fractions were obtained at the air/water interface by monolayer compression at constant temperature. The overlap surface concentrations were determined, and from these results the radius of gyration in two dimensions was calculated. The thermodynamic power of the toluene and the air/water interface for PTHPMM were estimated from the empirical relationship between the radius of gyration in two and three dimensions and the weight-average molecular weight.

Using banana to generate lactic acid through batch process fermentation.

We evaluated the usefulness of waste banana for generating lactic acid through batch fermentation, using Lactobacillus casei under three treatments. Two treatments consisted of substrates of diluted banana purée, one of which was enriched with salts and amino acids. The control treatment comprised a substrate suitable for L. casei growth. When fermentation was evaluated over time, significant differences (P<0.05) were found in the three treatments for each of five variables analyzed (generation and productivity of lactic acid, and consumption of glucose, fructose, and sucrose). Maximum productivity was (in g l(-1) h(-1)) 0.13 for the regular banana treatment, 1.49 for the enriched banana, and 1.48 for the control, with no significant differences found between the latter two treatments. Glucose consumption curves showed that L. casei made greater use of the substrate in the enriched banana and control treatments than in the regular banana treatment. For fructose intake, the enriched banana treatment showed significantly better (P<0.05) results than the regular one. Sucrose consumption was insignificant (P<0.05), probably because fermentation time was too short. Even when enriched, diluted banana purée is an ineffective substrate for L. casei, probably because it lacks nutrients.