RESUMEN
BACKGROUND: Despite civilization and progress, burns occur frequently in the world. Remarkable discoveries of wound healing mechanisms have been reported. On the other hand, long-term outcomes from burn injuries represent a barrier to improvement of patients' social, functional, and psychological condition. Lipofilling, described since the 1980s, currently is used for several clinical applications. This study aimed to verify whether lipofilling could ameliorate scar remodeling in three clinical cases. METHODS: Three adult patients with hemifacial hypertrophic scars and keloids resulting from severe burns 2 to 13 years previously were selected. The patients were treated by injection of adipose tissue harvested from abdominal subcutaneous fat and processed according to Coleman's technique. Two injections (with a 13-month interval between) were administered at the dermohypodermal junction. Histologic examination of scar tissue punch biopsies (hematoxylin-eosin staining) before and after the treatment was performed as well as magnetic resonance scan with contrast. RESULTS: The clinical appearance and subjective patient feelings after a 6-month follow-up period suggest considerable improvement in the mimic features, skin texture, and thickness. Histologic examination shows patterns of new collagen deposition, local hypervascularity, and dermal hyperplasia in the context of new tissue, with high correspondence to the original. CONCLUSIONS: The preliminary results show that lipofilling improves scar quality and suggest a tissue regeneration enhancing process.
Asunto(s)
Quemaduras , Cicatriz Hipertrófica , Queloide , Procedimientos de Cirugía Plástica , Tejido Adiposo , Adulto , Quemaduras/cirugía , Cicatriz/cirugía , HumanosRESUMEN
OBJECTIVE: To systematically examine the effects of dopaminergic agents (modafinil, armodafinil, pramipexole, methylphenidate, and amphetamines) on bipolar depression outcomes. METHODS: Meta-analysis of randomized controlled trials was performed to assess the efficacy and safety of treatment with dopaminergic agents in bipolar depression. In a secondary analysis, findings from both randomized controlled trials and high-quality observational studies were pooled by means of meta-analytic procedures to explore dopaminergic treatment-related new mania. RESULTS: Nine studies (1716 patients) were included in our meta-analysis of randomized controlled trials. Treatment with dopaminergic agents for bipolar depression was associated with an increase in both response (1671 individuals, RR 1.25, 95% CI 1.05 to 1.50) and remission rates (1671 individuals, RR 1.40, 95% CI 1.14, 1.71). There was no evidence of an increased risk of mood switch associated with this treatment (1646 individuals, RR 0.96, 95% CI 0.49, 1.89). Our secondary analysis (1231 individuals) yielded a cumulative incidence of mood switch of 3% (95% CI 1.0, 5.0) during a mean follow-up period of 7.5 months. CONCLUSIONS: Preliminary findings suggest that dopaminergic agents may represent a useful alternative for the treatment of bipolar depression, with no evidence for a related increase in the risk of mood destabilization during short-term follow-up.
Asunto(s)
Trastorno Bipolar/tratamiento farmacológico , Dopaminérgicos/uso terapéutico , Humanos , Resultado del TratamientoRESUMEN
In the case of high valuable individuals with very precious genetic material, widening the genetic pool including gametes with poor morphological characteristics, as cumulus-denuded oocytes (CDOs), could be an option. To improve the in vitro culture of low-competence feline CDOs, an enriched three-dimensional (3D) system in association with competent cumulus-oocyte complexes (COCs) was developed. For this purpose, domestic cat CDOs were cultured with or without companion COCs in the 3D barium alginate microcapsules. The overall viability and the meiotic progression of feline CDOs cocultured with COCs or cultured separately in 3D or in 2D (traditional microdrops) system were compared. The 3D system was able to support viability and meiotic resumption of the feline oocytes, as well as the 2D microdrops. In 3D microcapsules, the presence of COCs resulted in a higher viability of CDOs (91.1%, p < .05), than that obtained without COCs or in 2D microdrops (71.2% and 67.3%, respectively), but the percentages of meiotic resumption were similar of those of CDOs cultured separately (55.4% vs. 40.4%, p > .05). It is notable that the presence of CDOs seemed to enhance the meiotic progression of the associated COCs. In conclusion, the 3D barium alginate microcapsules are a suitable system for feline oocytes in vitro culture, but more specific enriched conditions should be developed to improve the CDOs full competence in vitro.
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Alginatos/farmacología , Células del Cúmulo/efectos de los fármacos , Técnicas de Maduración In Vitro de los Oocitos/instrumentación , Meiosis/efectos de los fármacos , Oocitos/efectos de los fármacos , Animales , Gatos , Técnicas de Cocultivo , Femenino , Ácido Glucurónico/farmacología , Ácidos Hexurónicos/farmacología , Técnicas de Maduración In Vitro de los Oocitos/veterinariaRESUMEN
In the last 30 years, encapsulation technology has been applied to different species to minimize the loss of spermatozoa after artificial insemination. In particular, the vehiculation of boar sperm cells in barium alginate membrane has proved a valid strategy to reduce the risk of polyspermy and optimize in vivo fertilizing yields. Controlled release of male gametes into the female genital tract has reduced the minimum fertilizing dose of spermatozoa. Notwithstanding these results, encapsulation has not yet reached commercial application, largely due to the additional costs of production. However, encapsulation could be useful in advanced reproductive technology, such as sex sorting, to store sorted boar semen. The controlled release of flow cytometrically sorted spermatozoa could be a promising strategy to reduce the number of cells necessary for each insemination and hence allow the widescale use of sex sorting in this species.
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Inseminación Artificial/veterinaria , Reproducción , Espermatozoides , Porcinos , Alginatos , Animales , Separación Celular , Femenino , Ácido Glucurónico , Ácidos Hexurónicos , Inseminación Artificial/métodos , Inseminación Artificial/tendencias , Masculino , Membranas Artificiales , Técnicas Reproductivas/tendencias , Técnicas Reproductivas/veterinaria , Preselección del Sexo/veterinaria , Espermatozoides/citologíaRESUMEN
Skin substitutes are epidermal, dermal or complete bilayered constructs, composed by natural or synthetic scaffolds and by adherent cells such as fibroblasts, keratinocytes or mesenchymal stem cells. Silk fibroin is a promising polymer to realize scaffolds, since it is biocompatible, biodegradable, and exhibits excellent mechanical properties in terms of tensile strength. Moreover, fibroin can be added of others components in order to modify the biomaterial properties for the purpose. The aim of this work is to prepare silk fibroin films for adipose-derived stem cell (ADSCs) culture as a novel feeder layer for skin tissue engineering. Pectin has been added to promote the protein conformational transition and construct strength, while glycerol as plasticizer, providing biomaterial flexibility. Eighteen formulations were prepared by casting method using fibroin, pectin (range 1-10% w/w), and glycerol (range 0-20% w/w); films were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry assay, to select the optimal composition. A stable fibroin conformation was obtained using 6% w/w pectin, and the best mechanical properties were obtained using 12% w/w glycerol. Films were sterilized, and human ADSCs were seeded and cultured for 15 days. Cells adhere to the support assuming a fibroblastic-like shape and reaching confluence. The ultrastructural analysis evidences typical active-cell features and adhesion structures that promote cell anchorage to the film, thus developing a multilayered cell structure. This construct could be advantageously employed in cutaneous wound healing or where the use of ADSCs scaffold is indicated either in human or veterinary field.
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Tejido Adiposo/citología , Fibroínas/química , Piel/citología , Células Madre/citología , Ingeniería de Tejidos/métodos , Rastreo Diferencial de Calorimetría , Células Cultivadas , Humanos , Espectroscopía Infrarroja por Transformada de Fourier , EsterilizaciónRESUMEN
Chronotype is a reliable biomarker for studying the influence of external zeitgebers on circadian entrainment. Assessment of chronotype variation in participants exposed to extreme photoperiods may be useful to investigate how changes in light-dark cycle modulate the circadian system. This study aimed to examine chronotype and sleep changes during a winter campaign at the Argentine Antarctic station Belgrano II. A sample of 82 men who overwintered in Antarctica completed the Munich Chronotype Questionnaire during March (daylight length: 18.6 h), May (daylight length: 2.8 h), July (daylight length: 0 h), September (daylight length: 14.5 h), November (daylight length: 24 h). The main results showed a decrease in sleep duration and a delay in chronotype and social jetlag during the polar night, highlighting the influence of social cues and the impact of the lack of natural light on circadian rhythms.
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Cronotipo , Trastornos del Sueño-Vigilia , Masculino , Humanos , Regiones Antárticas , Ritmo Circadiano , SueñoRESUMEN
Encapsulation of boar semen is a novel technique that allows insemination to be performed as a single intervention without the need to dilute the semen. The research reviewed in this paper shows that spermatozoa encapsulated in alginate are able to achieve the same fertility as two or three inseminations per oestrus using standard techniques and unencapsulated cells. The use of encapsulated spermatozoa is currently limited by the need for longer semen processing time and wastage of disposable material (catheters, plastic bottles, etc.). In this review, the advantages, the drawbacks and the future possibilities for artificial insemination with encapsulated spermatozoa in the sow are discussed, with the aim of applying this promising new methodology for the optimization of sow reproductive performance.
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Inseminación Artificial/veterinaria , Semen/fisiología , Manejo de Especímenes/veterinaria , Porcinos/fisiología , Alginatos , Animales , Femenino , Inseminación Artificial/métodos , Masculino , EmbarazoRESUMEN
A boar sperm encapsulation technology in barium alginate has been developed to enhance reproductive performances and spermatozoa preservation time; aim of this work was to evaluate the effect of in vitro sperm encapsulation on polyspermy as a function of storage time at 18 degrees C. A total number of 40 in vitro fertilization (IVF) tests were performed using encapsulated or diluted spermatozoa (20 IVF each treatment). Overall, 1288 in vitro matured oocytes were fertilized with spermatozoa stored at 24, 48 or 72 h at 18 degrees C for both treatments polyspermy and normospermy, and the non-penetration rates were assessed by optical microscopy. Results indicate a significant reduction in risk of polyspermic oocytes when spermatozoa are preserved in barium alginate membranes (incidence risk ratio: 0.766 with respect to diluted); such enhancement could be explained by lesser damage of sperm membranes achieved by encapsulation technology.
Asunto(s)
Fertilización In Vitro/veterinaria , Fertilización/fisiología , Preservación de Semen/veterinaria , Espermatozoides/fisiología , Porcinos , Animales , Masculino , Preservación de Semen/métodosRESUMEN
IL-1R8 is a member of Interleukin-1 receptor family acting as a negative regulator of inflammation reliant on ILRs and TLRs activation. IL-1R8 role has never been evaluated in acute bacterial mastitis. We first investigated IL-1R8 sequence conservation among different species and its pattern of expression in a wide panel of organs from healthy goats. Then, modulation of IL-1R8 during natural and experimental mammary infection was evaluated and compared in blood, milk and mammary tissues from healthy and Staphylococcus aureus infected goats. IL-1R8 has a highly conserved sequence among vertebrates. Goat IL-1R8 was ubiquitously expressed in epithelial and lymphoid tissues with highest levels in pancreas. IL-1R8 was down-regulated in epithelial mammary cells following S. aureus infection. Interestingly it was up-regulated in leukocytes infiltrating the infected mammary tissues suggesting that it could represent a target of S. aureus immune evasion.
Asunto(s)
Enfermedades de las Cabras/inmunología , Inmunidad Innata , Glándulas Mamarias Animales/microbiología , Mastitis/veterinaria , Receptores de Interleucina-8/genética , Infecciones Estafilocócicas/inmunología , Animales , Regulación hacia Abajo , Células Epiteliales/inmunología , Células Epiteliales/microbiología , Femenino , Enfermedades de las Cabras/microbiología , Cabras/microbiología , Inflamación , Glándulas Mamarias Animales/inmunología , Mastitis/inmunología , Mastitis/microbiología , Receptores de Interleucina-8/sangre , Staphylococcus aureus/inmunología , Regulación hacia ArribaRESUMEN
It is well established that different factors affect milk composition in cows and that milk composition, in turn, affect both technological and nutritional qualities. In this respect the comprehension of the metabolic variability of milk composition in relation to the lactation time as well as to the genetic background may be of paramount importance for the agri-food industries. In the present study we investigated the variations of the metabolic profiles during lactation in milks obtained from Friesian and autochthonous races from Northern Italy by 1H NMR metabolomics. Furthermore, the external factors influencing the milk composition were minimized: the cows were breeded in the same farm, were fed with the same diet and were paired for the lactation interval and lactation stage. Our results showed a difference in milk composition between races and in relation to late lactation. The PLS-DA analysis permitted to distinguish the Friesian and autochthonous cow milks at the investigated different lactation times. Interestingly, the metabolites significantly involved into the discrimination between races appeared to be also technological property parameters, highlighting the importance of maintaining the biodiversity of cow breeds. Therefore, NMR-based metabolomics of milk could represent an informative tool to identify metabolites involved in milk quality both from a nutritional and industrial perspective.
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Lactancia/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Metabolómica/métodos , Leche/química , Leche/metabolismo , Alimentación Animal , Animales , Bovinos , Femenino , Análisis de los Alimentos/métodos , Análisis de los Alimentos/estadística & datos numéricos , Italia , Espectroscopía de Resonancia Magnética/estadística & datos numéricos , Análisis MultivarianteRESUMEN
Zearalenone (ZEA) is a fusariotoxin naturally occurring in crops with known estrogenic activity in swine, the most sensitive known species. The metabolism by swine of ZEA, principally into alpha-zearalenol (alpha-ZOL), is considered as a bio-activation because of its high affinity with estrogenic receptors. Discordant data on male reproductive failures induced by ZEA in vivo are described. In this study, we evaluated the effects to boar spermatozoa when they are exposed in vitro to ZEA and its derivatives (alpha-ZOL, beta-ZOL). We analyzed viability, apoptosis (terminal deoxynucleotidyltransferase dUTP nick end-labelling (TUNEL)), sperm chromatin stability (sperm chromatin structure assay (SCSA)) and motility (using computer-aided sperm analysis (CASA)). Each mycotoxin influenced a specific function of spermatic cells. alpha-Zearalenol and ZEA, at picomolar levels, negatively influenced chromatin structure stability and viability, respectively, whereas beta-ZOL negatively influenced the sperm motility at micromolar levels. This study is the first using these direct measures of sperm integrity to show the potential for an adverse effect of ZEA exposure on boar fertility.
Asunto(s)
Estrógenos no Esteroides/toxicidad , Espermatozoides/efectos de los fármacos , Zearalenona/toxicidad , Zeranol/análogos & derivados , Animales , Apoptosis , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Cromatina/efectos de los fármacos , Masculino , Motilidad Espermática/efectos de los fármacos , Espermatozoides/fisiología , Porcinos , Zeranol/toxicidadRESUMEN
A cell encapsulation technology in alginate has been developed with the aim of obtaining cell controlled release or three-dimensional cultures. The aim of this work is to verify the predictability of alginate capsules for large-scale production by Good Manufacturing Practice (GMP) standardized procedures in a cell factory. A cell-free capsule model was performed following the GMP guidelines: an opaque agent suspension in a bivalent cation solution (Ca(2+), Ba(2+), Sr(2+)) was dropped in a sodium alginate solution, obtaining capsules presenting a liquid core surrounded by a gel alginate membrane. The concentration of the ion, and the treatment with protamine, can considerably vary the characteristics of the capsules (weight, whole diameter, core diameter, gel capsule thickness, capsule strength). It is therefore possible to optimize the performance of the capsules, relating the molecular structure and size of the polymeric membrane to the desired functional properties. Technological resources are available for large-scale cell encapsulation intended for advanced therapies (gene therapy, somatic cell therapy and tissue engineering) in a cell factory, following GMP guidelines.
Asunto(s)
Alginatos/química , Membranas Artificiales , Ingeniería de Tejidos/métodos , Ingeniería de Tejidos/normas , Bacterias/efectos de los fármacos , Cápsulas , Hongos/efectos de los fármacos , Geles , Ácido Glucurónico/química , Ácidos Hexurónicos/química , Protaminas/farmacologíaRESUMEN
Pentraxin 3 is the prototypic long pentraxin and is produced by different cell populations (dendritic cells, monocytes/macrophages, endothelial cells, and fibroblasts) after pro-inflammatory stimulation. Different studies demonstrated the up-regulation of PTX3 during mastitis in ruminants, but its role is still unknown. We first investigated the conservation of PTX3 sequence among different species and its pattern of expression in a wide panel of organs from healthy goats. We studied the modulation of PTX3 during natural and experimental mammary infection, comparing its expression in blood, milk and mammary tissues from healthy and Staphylococcus aureus infected animals. We confirmed the high conservation of the molecule among different species. Goat PTX3 was expressed at high levels in bone marrow, mammary gland, aorta, rectum, pancreas, skin and lungs. PTX3 was up-regulated in epithelial mammary cells and in milk cells after S. aureus infection, suggesting that it represents a first line of defense in goat udder.
Asunto(s)
Proteína C-Reactiva/metabolismo , Cabras/metabolismo , Componente Amiloide P Sérico/metabolismo , Infecciones Estafilocócicas/metabolismo , Staphylococcus aureus/metabolismo , Regulación hacia Arriba/fisiología , Animales , Células Epiteliales/metabolismo , Femenino , Perfilación de la Expresión Génica/veterinaria , Humanos , Mastitis/metabolismo , Mastitis/veterinaria , Rumiantes/metabolismoRESUMEN
Concentration of progesterone in milk may be used to predict pregnancy status of dairy cattle by the 21st day after insemination. However, the accuracy of this method may be affected by fat-solubility of progesterone and sample storage conditions. After coagulation of a milk sample with rennet, an alternative method is to quantify progesterone concentration in whey with a novel, validated EIA. In this experiment, a receiver operating characteristic (ROC) analysis was performed to estimate the optimal discrimination point for whey progesterone concentration, using a sample of 991 Friesian cows evaluated between the 42nd and 44th day after insemination. Cows also were diagnosed for pregnancy by rectal palpation at this time. The overall conception rate at palpation was 57%. ROC analysis indicated that 259 pg/mL progesterone in whey was the most effective cutoff to discriminate correctly between pregnant and non-pregnant cows. Using this point for prediction, sensitivity was 98.2%, specificity was 70.9% and the area under ROC curve was 0.859, levels generally considered to denote moderate accuracy. The negative likelihood ratio at the cutoff of 259 pg/mL was 0.02, indicating satisfactory performance in detecting negative subjects, while the positive likelihood ratio (+LR=3.37) suggested average performance. In conclusion, EIA of progesterone concentration in whey is a viable method for predicting pregnancy status in cows. However, operators should take management objectives for the herd into account in determining the cutoff point and also considering important influencing variables such as conception rate in the herd. This method can provide diagnostic support for efforts to improve reproductive success, especially in low-fertility herds.
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Bovinos/fisiología , Leche/química , Pruebas de Embarazo/veterinaria , Progesterona/análisis , Curva ROC , Análisis de Varianza , Animales , Femenino , Inseminación Artificial/veterinaria , Palpación , Embarazo , Recto , Sensibilidad y Especificidad , Factores de TiempoRESUMEN
Despite the great potential application of sex-sorted spermatozoa in swine, the technology is not practiced in the pig industry because of technical factors and species-specific issues. The susceptibility of boar spermatozoa to stresses induced by the sorting procedure, the relative slowness of the sex-sorting process together with the high sperm numbers required for routine artificial insemination in pig are some of the main factors limiting the commercial application of this technology in pigs. This review briefly describes the damage to spermatozoa during sex sorting, focusing on an additional limiting factor: increased susceptibility of sexed boar spermatozoa to injuries induced by liquid storage and cryopreservation that, in turn, impairs sperm quality leading to unsatisfactory results in vivo. Strategies to extend the lifespan of sex-sorted boar spermatozoa and to improve their fertilizing ability after liquid storage or cryopreservation need to be implemented before this technology can be used in pig farms. In this regard, encapsulation in barium alginate membranes could be a promising technique to optimize the in vivo use of sexed boar spermatozoa, by protecting, targeting, and controlling the release of sperm into the female genital tract.
Asunto(s)
Preservación de Semen/veterinaria , Semen/fisiología , Preselección del Sexo , Porcinos/fisiología , Animales , Femenino , Inseminación Artificial/veterinaria , MasculinoRESUMEN
Granulosa cells from bovine and porcine ovaries were cultured either in monolayer or in follicle-like barium alginate capsules for 6 days. Morphological investigation by electron scanning microscopy indicated that culture in a three-dimensional (3D) system allows self-organization of spherical-polyhedral shape cells. The luteinization index (progesterone:17beta-estradiol ratio) was significantly higher for monolayer cells than for the 3D cell culture system, confirming the results of morphological analysis and indicating more physiological growth. The encapsulated 3D culture system appears to be a promising way of obtaining in vitro maturation and development of follicles and oocytes.
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Células de la Granulosa , Membranas Artificiales , Modelos Biológicos , Ingeniería de Tejidos , Alginatos , Animales , Bovinos , Técnicas de Cultivo de Célula , Femenino , Ácido Glucurónico , Ácidos Hexurónicos , Microscopía Electrónica de Rastreo , Oocitos , Protaminas , Porcinos , Factores de TiempoRESUMEN
Three-dimensional culture systems in barium alginate capsules can be employed to maintain primary granulosa cells in an undifferentiated state for almost 6 days. This is due to a self-organization of cells in a pseudofollicular structure. The transfection of primary granulosa cells is a necessary condition when employing these culture systems for several purposes, for example as an in vitro toxicity test or the development of oocytes or zygotes. In this work, the feasibility of two transient transfection techniques (liposome-mediated and electroporation) was assessed in primary porcine granulosa cells after a 6-day culture in an artificial extracellular matrix (barium alginate membrane). Human recombinant green fluorescent protein was chosen as a molecular readout, and protein expression was assessed after 48 hours from transfection. Liposome-mediated transfection gave low transfection levels, with increasing yields from 2 to 12 microgDNA/ml of medium; the maximum percentage (85.7%) was reached at 12 microgDNA/ml of medium. Electroporation-mediated transfection yields were higher: the best results (81.7% of transfected cells) were achieved with two 50V pulses and 12 microg/ml DNA. The application of a single or double pulse (50V) at 4 mgDNA/ml gave negligible results. These results indicate that primary granulosa cell cultured in barium alginate capsules can be transfected by electroporation with high transfection yields.
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Alginatos/química , Células de la Granulosa/metabolismo , Animales , Cationes/química , Técnicas de Cultivo de Célula , Células Cultivadas , ADN/genética , Portadores de Fármacos , Electroporación , Femenino , Ácido Glucurónico/química , Ácidos Hexurónicos/química , Liposomas , Microscopía Fluorescente , Ovario/química , Ovario/citología , Porcinos , TransfecciónRESUMEN
A quick and successful encapsulation method of swine spermatozoa is described: hydroxypropylmethylcellulose and calcium chloride were added to the sampled ejaculate swine sperm (sperm-rich fraction: creamy white) and then this suspension was dropped into an aqueous solution of sodium alginate. In order to obtain different capsule thicknesses, different calcium chloride concentrations were used. The influence of different formulations on in vitro spermatozoa release behavior and on the mechanical properties has been studied. In vitro sperm kinetics (motility and average velocity) have been determined. The results obtained from motility and average velocity tests of treated seminal material are promising, especially if the difficulty of preservation of swine spermatozoa compared to bovine sperm is considered. The different membranes obtained from the different calcium concentrations have had an influence on mechanical properties and on the release profile of spermatozoa from the capsules, and therefore, it is possible to modulate the release rate of the cells.
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Alginatos , Cápsulas , Semen/fisiología , Espermatozoides/fisiología , Animales , Materiales Biocompatibles/química , Cápsulas/química , Bovinos , Preparaciones de Acción Retardada , Ácido Glucurónico , Ácidos Hexurónicos , Masculino , Microscopía Electrónica de Rastreo , Motilidad Espermática , PorcinosRESUMEN
Swine spermatozoa were encapsulated in barium alginate and protamine-barium alginate membranes to lengthen their preservation time and to provide a means of controlling their release. Precocious acrosome reactions and secondary anomalies were measured as indices of semen quality. These characteristics were observed for two forms of encapsulated spermatozoa when stored at 18 and 38 degrees C for 24 h and for semen diluted in a classical extender at both temperatures. The results indicate that encapsulation enhances semen preservation, providing protection against membrane damage upon dilution. The effect is even more evident at the higher temperature (38 degrees C), where cell metabolism is higher. An in vitro release test of spermatozoa showed a massive cell delivery from barium alginate capsules within 6 h, and a slow release from protamine-barium alginate capsules. The properties of spermatozoa 24 h after release did not differ from the semen stored at the same temperature in capsules, indicating that the release process does not impair semen quality.
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Semen/metabolismo , Espermatozoides/metabolismo , Alginatos/síntesis química , Alginatos/farmacocinética , Animales , Preparaciones de Acción Retardada/química , Preparaciones de Acción Retardada/farmacocinética , Composición de Medicamentos , Almacenaje de Medicamentos/métodos , Ácido Glucurónico , Ácidos Hexurónicos , Masculino , PorcinosRESUMEN
The alkaline hydrolysis of title esters possessing acidic leaving groups follows an E1cB mechanism involving the participation of an "extra extended" p-oxo ketene intermediate. For the hydrolysis of the 2,4-dinitrophenyl ester kinetic data, activation parameters and trapping of the intermediate clearly indicate that the dissociative pathway carries the reaction flux. Break in the Bronsted plot of the apparent second-order rate constants versus the pK(a) of the leaving group suggests that the reaction mechanism changes from E1cB to B(Ac)2 for esters having pK(a) higher than about 6.