An extracellular acetylcholinesterase produced by Aeromonas hydrophila is a major lethal toxin for fish

A hitherto unrecognised lethal toxin from the extracellular products (ECP) of Aeromonas hydrophila is described. The pure toxin was 300 times more toxic than the crude ECP and is the most toxic substance so far described from this bacterium, with a minimum lethal dose of 0.05 micrograms g-1 fish. The toxin had high acetylcholinesterase activity and occurred in native ECP as a monomeric 15.5 kDa polypeptide. The purified toxin had five isoelectric focusing forms ranging from pl 4.45 to 4.70. The ECP of each of six strains of A. hydrophila isolated from fish possessed acetylcholinesterase activity suggesting that the toxin is common in this species. The toxin was not a cytolysin and produced no gross pathology in injected fish. Its enzymic nature, low lethal dose, lack of tissue pathology and its apparent narcotic effect suggest that this toxin may act upon the central nervous system of the fish.     

Virus persists in beta cells of islets of Langerhans and infection is associated with chemical manifestations of diabetes. II. Morphologic observations.

Persistence of lymphocytic choriomeningitis (LCM) virus in the islets of Langerhans was associated with mild hyperglycemia and abnormal glucose tolerance test results. Early histopathologic events consisted of occasional perivascular inflammatory mononuclear cells around both islet and acinar cells. Morphometric studies showed an increase in the size of islets from virus-infected mice. By electron microscopy, LCM virions were found within infected beta cells. Cytolytic injury of beta cells was minimal and did not account for the abnormalities of glucose metabolism. In contrast to the findings in islets, ultrastructural studies of acinar cells revealed LCM virions in abundance, vacuolar degeneration, and intracytoplasmic inclusions. This study extends the previous observation that LCM virus infection may persist in beta cells of the islets of Langerhans without causing structural injury but be associated with abnormalities resembling the chemical and histopathologic features of the early stage of Type II (adult-onset) human diabetes mellitus.     

Isolation and purification of two immunodominant antigens from Nocardia brasiliensis.

Two immunogenic proteins from a crude extract of Nocardia brasiliensis were purified to homogeneity. A 61-kDa protein (P61) was isolated from a 50% ammonium sulfate precipitate in two steps. Initially, P61 was obtained by electroelution in a 10% nondenatured preparative polyacrylamide gel electrophoresis (PAGE). In a second step, the eluate from the nondenatured gel was run in a 12% sodium dodecyl sulfate (SDS) preparative polyacrylamide gel. After elution, a single band was demonstrated by SDS-PAGE and Western blot (immunoblot). Also, a 24-kDa immunogenic protein (P24) was isolated by gel filtration in a Sephadex G-100 column and then by electroelution in a 12% nondenatured polyacrylamide gel. In a previous paper, we showed by Western blot assays that these proteins are recognized by the sera of mycetoma patients and not by sera from mycobacterial-infected or healthy individuals. We consider these proteins to be good candidates for the study of the host-parasite relationship in nocardial infections. The possible clinical application of these purified antigens in a serological diagnosis is discussed.     

Microplate technique to determine hemolytic activity for routine typing of Listeria strains.

Because the hemolysis produced by Listeria monocytogenes and Listeria seeligeri on blood agar is frequently difficult to interpret, we developed a microplate technique for the routine determination of hemolytic activity with erythrocyte suspensions. This microtechnique is a simple and reliable test for distinguishing clearly between hemolytic and nonhemolytic strains and could be used instead of the CAMP (Christie-Atkins-Munch-Petersen) test with Staphylococcus aureus in the routine typing of Listeria strains. Furthermore, our results suggest that the quantitation of the hemolytic activity of the Listeria strains, along with the D-xylose, L-rhamnose, and alpha-methyl-D-mannoside acidification tests, allows the differentiation of L. monocytogenes, L. seeligeri, and Listeria ivanovii. We also observed that the treatment of erythrocytes with crude exosubstances of rhodococcus equi, Pseudomonas fluorescens, Acinetobacter calcoaceticus, and S. aureus enhanced the hemolytic activity of all Listeria strains with this characteristic.     

Clearance of Theiler's virus infection depends on the ability to generate a CD8+ T cell response against a single immunodominant viral peptide

Theiler's murine encephalomyelitis virus (TMEV) induces a chronic demyelinating disease in the central nervous system of susceptible mice. Resistance to persistent TMEV infection maps to he D locus of the major histocompatibility complex suggesting a prominent role of antiviral CTL in the protective immune response. Introduction of the D(b) gene into the FVB strain confers resistance to this otherwise susceptible mouse line. Infection of the FVB/D(b) mouse with TMEV provides a model where antiviral resistance is determined by a response elicited by a single class I molecule. Resistant mice of the H-2(b) haplotype mount a vigorous H-2D(b)-restricted immunodominant response to the VP2 capsid protein. To investigate the extent of the contribution of the immunodominant T cell population in resistance to TMEV, FVB/D(b) mice were depleted of VP2-specific CD8(+) T cells by peptide treatment prior to virus infection. Peptide-treated mice were not able to clear the virus and developed extensive demyelination. These findings demonstrate that the D(b)-restricted CD8(+) T cells specific for a single viral peptide can confer resistance to TMEV infection. Our ability to manipulate this cellular response provides a model for investigating the mechanisms mediating protection against virus infection by CD8(+) T cells.     

Pregnancy with frozen-thawed and fresh testicular biopsy after motile and immotile sperm microinjection, using the mechanical touch technique to assess viability

BACKGROUND: There are few reports of pregnancy using immotile sperm, and none using a purely mechanical assessment of viability. METHODS: In this pilot study, we retrospectively analysed 66 cycles in 61 patients with determinant male factor, recording rates of fertilization, implantation, normal pregnancy and take-home babies achieved with ICSI. Sperm selection was based on morphologically normal appearance under the inverted microscope. Viability of immotile spermatozoa was assessed by the mechanical touch technique to observe tail flexibility and tail shape recovery. RESULTS: Of 17 ICSI cycles using frozen-thawed testicular sperm, six microinjected with immotile and 11 with motile sperm, we achieved fertilization rates of 65.7 and 74.3%, respectively, and five pregnancies (two and three, respectively). Of 49 ICSI cycles using fresh testicular sperm, 10 microinjected with immotile and 39 with motile sperm, we achieved fertilization rates of 73.4 and 64.4%, respectively, and 12 pregnancies (three and nine, respectively). CONCLUSIONS: Immotile (fresh and frozen-thawed) testicular sperm of normal morphological appearance can be used to achieve clinical pregnancy with ICSI. Our results strongly suggest that immotile sperm viability can be assessed by the mechanical touch technique.     

Effect of platelet-derived growth factor on the development and persistence of asbestos-induced fibroproliferative lung disease.

Platelet-derived growth factor (PDGF) isoforms and PDGF receptor-alpha are upregulated in fibroproliferative lesions in response to asbestos exposure. To examine the functional role of PDGF in asbestos-induced lung disease, we have evaluated the impact of PDGF-B overexpression in the lung on the development of pulmonary fibrosis induced by asbestos inhalation. Transgenic mice expressing PDGF-B from the surfactant protein C promoter and wild-type C57BL/6 mice were exposed to aerosolized chrysotile asbestos fibers via three different exposure regimens: 3 consecutive days to 9 mg/m(3), once a week for 5 weeks to 12 mg/m(3), or once a week for 8 weeks to 11 mg/m(3). The 3-day exposure did not produce fibroproliferative lesions in SPC-PDGFB or wild-type mice, indicating that PDGF expression did not increase susceptibility to a subthreshold dose of asbestos. Transgenic and wild-type mice subjected to the 5-week exposure protocol exhibited similar fibrogenic lesions histologically 48 hours and 8 weeks postexposure, but lungs from transgenic mice had elevated lung hydroxyproline content 8 weeks postexposure relative to wild-type mice. In addition, SPC-PDGFB transgenic mice developed pronounced thickening of arterioles following the 5-week exposure regimen. Mice exposed to asbestos for 8 weeks and examined 10 months later showed pronounced, diffuse fibrotic lesions of terminal bronchioles and alveolar ducts, but no histological differences between transgenic and nontransgenic mice were observed. These results indicated that PDGF-B overexpression can stimulate increased collagen deposition and vascular smooth muscle hyperplasia following asbestos inhalation and that a limited exposure (8 times) to chrysotile aerosol can produce long-lasting fibrotic lesions. The 8-week exposure regimen provides an animal model that encompasses an important aspect of human asbestosis-i.e., persistence of fibrosis for long periods after cessation of asbestos exposure.