Effect of apo-lactoferrin on leukotoxin and outer membrane vesicles of Mannheimia haemolytica A2.

Mannheimia haemolytica serotype A2 is the principal cause of pneumonic mannheimiosis in ovine and caprine livestock; this disease is a consequence of immune suppression caused by stress and associated viruses and is responsible for significant economic losses in farm production worldwide. Gram-negative bacteria such as M. haemolytica produce outer membrane (OM)-derived spherical structures named outer membrane vesicles (OMVs) that contain leukotoxin and other biologically active virulence factors. In the present study, the relationship between M. haemolytica A2 and bovine lactoferrin (BLf) was studied. BLf is an 80 kDa glycoprotein that possesses bacteriostatic and bactericidal properties and is part of the mammalian innate immune system. Apo-BLf (iron-free) showed a bactericidal effect against M. haemolytica A2, with an observed minimal inhibitory concentration (MIC) of 16 µM. Sublethal doses (2-8 µM) of apo-BLf increased the release of OMVs, which were quantified by flow cytometry. Apo-BLf modified the normal structure of the OM and OMVs, as observed through transmission electron microscopy. Apo-BLf also induced lipopolysaccharide (LPS) release from bacteria, disrupting OM permeability and functionality, as measured by silver staining and SDS and polymyxin B cell permeability assays. Western blot results showed that apo-BLf increased the secretion of leukotoxin in M. haemolytica A2 culture supernatants, possibly through its iron-chelating activity. In contrast, holo-BLf (with iron) did not have this effect, possibly due to differences in the tertiary structure between these proteins. In summary, apo-BLf affected the levels of several M. haemolytica virulence factors and could be evaluated for use in animals as an adjuvant in the treatment of ovine mannheimiosis.

Mannheimia haemolytica A2 secretes different proteases into the culture medium and in outer membrane vesicles.

Respiratory diseases in ruminants have a significantly negative impact on the worldwide economy. The bacterium Mannheimia haemolytica is involved in pneumonic infections in bovine and ovine. In gram-negative bacteria, six secretion systems related to the colonization process and host tissue damage have been reported. In addition, in the last two decades, the production of outer membrane vesicles has been studied as a different bacterial strategy to release virulence factors, such as exotoxins, lipopolysaccharides, and proteases. However, in M. haemolytica serotype A2, protease secretion and release in vesicles have not been reported as virulence mechanisms. The aim of this work was to identify proteases released into the culture supernatant and in vesicles of M. haemolytica A2. Our results showed evident differences in the molecular mass and activity of proteases present in culture supernatants and outer membrane vesicles based on zymography assays. The biochemical characterization of M. haemolytica proteases revealed that the main types were cysteine and metalloproteases. A specific metalloprotease of 100 kDa was active in the culture supernatants, but it was not active and was found in low quantities in vesicles. Proteases could be an important virulence factor during the infectious pneumonic process led by M. haemolytica.

Airway pressure release ventilation reduces conducting airway micro-strain in lung injury.

BACKGROUND: Improper mechanical ventilation can exacerbate acute lung damage, causing a secondary ventilator-induced lung injury (VILI). We hypothesized that VILI can be reduced by modifying specific components of the ventilation waveform (mechanical breath), and we studied the impact of airway pressure release ventilation (APRV) and controlled mandatory ventilation (CMV) on the lung micro-anatomy (alveoli and conducting airways). The distribution of gas during inspiration and expiration and the strain generated during mechanical ventilation in the micro-anatomy (micro-strain) were calculated. STUDY DESIGN: Rats were anesthetized, surgically prepared, and randomized into 1 uninjured control group (n = 2) and 4 groups with lung injury: APRV 75% (n = 2), time at expiration (TLow) set to terminate appropriately at 75% of peak expiratory flow rate (PEFR); APRV 10% (n = 2), TLow set to terminate inappropriately at 10% of PEFR; CMV with PEEP 5 cm H2O (PEEP 5; n = 2); or PEEP 16 cm H2O (PEEP 16; n = 2). Lung injury was induced in the experimental groups by Tween lavage and ventilated with their respective settings. Lungs were fixed at peak inspiration and end expiration for standard histology. Conducting airway and alveolar air space areas were quantified and conducting airway micro-strain was calculated. RESULTS: All lung injury groups redistributed inspired gas away from alveoli into the conducting airways. The APRV 75% minimized gas redistribution and micro-strain in the conducting airways and provided the alveolar air space occupancy most similar to control at both inspiration and expiration. CONCLUSIONS: In an injured lung, APRV 75% maintained micro-anatomic gas distribution similar to that of the normal lung. The lung protection demonstrated in previous studies using APRV 75% may be due to a more homogeneous distribution of gas at the micro-anatomic level as well as a reduction in conducting airway micro-strain.

Episodic spontaneous hypothermia: a periodic childhood syndrome.

Episodic spontaneous hypothermia is an infrequent disorder, with unknown pathogenic mechanisms. A systemic cause or underlying brain lesion has not been found for the disease. We report four new patients, 3-9 years old, with episodic hypothermia lower than 35 degrees C, marked facial pallor, and absent shivering. The episodes could last a few hours or four days, and recurred once a week or every 2-3 months. Two patients also demonstrated bradycardia, mild hypertension, and somnolence during the events; in one of them, profuse sweating was also a feature, and all four presented with either headache, a periodic childhood syndrome, or both (recurrent abdominal pain, cyclic vomiting, or vertigo). Three patients reported a family history of migraine. Neurologic examination, endocrine function, and imaging studies were normal. Migraine prophylactic therapy was of moderate efficacy. Spontaneous resolution was observed in one patient. The clinical characteristics of the syndrome allow for its inclusion as a childhood periodic syndrome related to migraine.

Incidencia de abdomen agudo en el departamento de pediatría / Incidence of acute abdomen in the Pediatric Departament

El presente trabajo referido a abdomen agudo de tipo retrospectivo, descriptivo de seguimiento longitudinal, fue realizado en el Departamento de Pediatría del Hospital Materno Infantil Germán Urquidi de la Ciudad de Cochabamba. Se hizo un revisión de aproximadamente 3038 historias clínicas de todos los niños internados en el departamento de pediatría en el periódo comprendido entre los meses de Enero de 1993 a Diciembre de 1994, de los cuales 130 historias correspondieron a abdomen agudo (4.3 por ciento) correspondieron el universo en estudio. Se tomaron en cuenta las variables de edad sexo, procedencia, grado nutricional, estado inmunitario, presentación clínica, conducta y diagnóstico. Los datos encontrados indican que en la incidencia del abdomen agudo el cuadro predominante fue la apendicitis aguda con un 40 por ciento, el sexo mas afectado el masculino con 68 por ciento, la conducta tomada en el tipo de patología en un gran porcentaje fue quirúrgica (77.7 por ciento) y las complicaciones presentadas fueron muy bajas.