Molecular and biochemical mechanisms ofPasteurella haemolyticaleukotoxin-induced cell death

Pasteurella haemolyticaleukotoxin (LKT) is a member of the RTX family of pore-forming toxins that kill bovine immune cells. Several studies have suggested that RTX toxins kill target cells by the induction of apoptosis. In the present study, BL3 bovine leukaemia cells were exposed to LKT and assessed by molecular and flow cytometric techniques that measure different aspects of apoptotic cell death. The intoxicated cells demonstrated morphological, light scatter and Hoechst 33258 staining characteristics consistent with cells undergoing apoptosis. The cells also exhibited internucleosomal DNA fragmentation and poly (ADP-ribose) polymerase (PARP) cleavage, both indicators of apoptosis. LKT-treated cells bound annexin-V-FITC indicating that phosphatidylserine groups were translocated from the inner to the outer leaflet of the cell membrane. The effect of LKT on cells was dose dependent and inhibitable by incubation with anti-LKT monoclonal antibody. Finally, an early step for induction of apoptosis appears to be the binding of LKT to a β2 integrin since pre-incubating cells with anti-β2 integrin antibodies inhibited LKT-induced apoptosis. This study provides new insights into understanding the pathogenesis of bovine pasteurellosis and could lead to the development of both preventative and therapeutic strategies for disease management.     

Further investigation of the association between gastroesophageal reflux and bronchoconstriction

A double-blind modification of the intraesophageal acid perfusion challenge (Bernstein procedure) was performed in asthmatic subjects with and without gastroesophageal reflux, nonasthmatic subjects with reflux, and normal subjects. Conventional spirometric functions and total respiratory resistance (Rrs) were measured prior to and after the infusion. There were no changes in pulmonary functions except in the asthmatic subjects who had had a positive add challenge. The greatest changes occurred in Rrs, which increased significantly with reflux symptoms (p < 0.01) and decreased toward baseline (p < 0.05) when these symptoms were relieved with antacids. The response was even greater in asthmatic subjects who associated reflux symptoms with attacks of asthma. These results support previous findings that acid reflux symptoms could cause a bronchoconstrictive response in certain asthmatic patients.     

Experimenter Expectancy Effects in Frontal EMG Conditioning

Nonspecific factors such as placebo or expectancy effects may materially influence therapeutic outcome in EMG relaxation training. Yet, controlling for the expectations of experimenters has received little attention even though Rosenthal's Experimenter Expectancy Effect is well-documented. This study examined the effects of experimenter expectancy on frontal EMG conditioning. During training, experimenters were given either no expectancy or led to believe that EMG conditioning would he either difficult (low expectancy) or easy (high expectancy) to achieve. Then, the three groups of experimenters collected data from subjects undergoing 20 min of either contingent or noncontingent reinforcement for frontal EMG decreases. Postexperimental credibility checks indicated that experimenters were unaware they were being studied but could identify their expectancy condition when informed of the three conditions. Differential EMG behavior was observed between groups conditioned by experimenters with no expectancies, with contingent subjects achieving significantly lower EMG levels than noncontingent subjects. Differences were not exhibited, however, between contingent and noncontingent subjects trained by experimenters with either low or high expectancies. These findings suggest that experimenters with prior expectations may covertly communicate to subjects response sets that interfere with acquisition of differential EMG behavior.     

Latency of multiple skin conductance responses in differential classical conditioning

Latencies of multiple skin conductance responses were observed in 30 female undergraduate students who participated in a classical differential conditioning experiment employing a 10 sec interstimulus interval (ISI). Responses occuring in both the early and late portions of the ISI were examined. Pairing delayed the onset of early responses and hastened the onset of responses occuring later in the ISI. Additionally, the latency changes observed did not appear to be an artifact of the higher response frequencies typically associated with conditioning.     

Comparison of complement fixation and hemagglutination inhibition assays for detecting antibody responses following influenza virus vaccination

Complement fixation (CF) was compared to hemagglutination inhibition (HI) as a method for identifying antibody responses to influenza virus vaccination. CF assays were performed at two different laboratories using paired (pre- and postvaccination) sera from 38 vaccinated laboratory employees; HI assays were performed at a third laboratory. As expected, most vaccinees (31/38 = 82%) responded to at least one of three influenza virus antigens as measured by HI. In contrast, only 21% (8/38) of vaccinees showed a response by CF at laboratory 1, and only 29% (11/38) showed a response by CF at laboratory 2. These findings indicate that due to low sensitivity, CF assays should not be used to assess the antibody response to influenza virus vaccination.     

Evaluation of a western blot method for the detection of Yersinia antibodies: evidence of serological cross-reactivity between Yersinia outer membrane proteins and Borrelia burgdorferi

Yersinia enterocolitica and Yersinia pseudotuberculosis have been identified as causative organisms of reactive arthritis in humans. We evaluated a Western blot assay which uses Yersinia outer membrane proteins as antigens for the detection of Yersinia antibodies as a replacement for the complement fixation (CF) assay. Clinical agreement, sensitivity, and specificity were determined by testing 19 positive and 21 negative serum samples by the CF assay, Western blot assay, and enzyme-linked immunosorbent assay (ELISA). The CF assay and ELISA were compared to the Western blot assay, which was the reference method used in this study. Sera with antibodies that could potentially cross-react with Yersinia were also tested by the Western blot assay. The agreement, sensitivity, and specificity of the CF method were 61%, 26%, and 95%, respectively; and those for the ELISA were 89%, 95%, and 82%, respectively. The prevalences of Yersinia antibodies in 50 healthy donors were 6% for immunoglobulin G (IgG), 2% for IgA, and 2% for IgM. Sera positive for Bartonella henselae, Brucella, Chlamydia pneumoniae, and Rickettsia rickettsii antibodies showed cross-reactivity by the Western blot assay. The highest cross-reactivity was observed with Borrelia burgdorferi; 5 of 11 (45%) specimens were cross-reactive by the IgM-specific assay. Overall, the Western blot assay performs acceptably and is more sensitive than the CF assay, warranting replacement of the CF assay in the laboratory. Due to the evidence of cross-reactivity, particularly with B. burgdorferi, which can cause an oligoarthritis similar to reactive arthritis, the diagnosis of reactive arthritis should be based on clinical findings and complete serologic analysis of the potential causative infectious pathogens.     

Ultrastructural Changes Suggestive of Focal Segmental Glomerulosclerosis in Atypical Minimal Change Nephrotic Syndrome

In an attempt to recognize early stages of focal segmental glomerulosclerosis (FSGS) in patients with a clinical course suggesting a diagnosis other than minimal change disease (MCD) and normal histology, or minor, nondiagnostic changes on light microscopy (LM), we used a protocol for systematic and extensive electron microscopy (EM) examination of kidney biopsies obtained from such patients. By this method ultrastructural pathology was found in 8 patients. These changes were localized, involving only portions of single glomerular segments. The findings included mild to moderate increase of the mesangial matrix, focal wrinkling of the capillary basement membrane, and early obliteration of the normal architecture of individual capillary loops, as well as electron-dense deposits in a mesangial and subendothelial distribution. Of these 8 patients, 2 are at present in remission without therapy (in 1, following therapy with cyclophosphamide); 3 are in remission on steroid therapy; 1 developed massive proteinuria during pregnancy, after a spontaneous remission lasting almost 2 years; 1 patient advanced to terminal renal failure 3 1/2 years after biopsy; and 1 died of sepsis 1 month after biopsy. We believe that the ultrastructural changes found may represent early or mild FSGS and that the protocol described can add valuable information in clinically worrisome patients in whom renal histology appears normal.     

Airway obstruction due to massive lingual oedema following cleft palate surgery

The Pierre Robin syndrome consists of micrognathia, pseudo-macroglossia, glossoptosis and a high arched or cleft palate. Difficult intubation of the trachea and associated abnormalities such as congenital heart disease are well known complications of this syndrome. Intraoral surgery (such as cleft palate repair and palatoplasty) can also be technically difficult for the surgeon resulting in prolonged retraction on the tongue with a mouth gag to provide adequate surgical exposure. We report a case where massive lingual oedema following a cleft palate repair resulted in life-threatening airway obstruction.