TYLCSV DNA, but not infectivity, can be transovarially inherited by the progeny of the whitefly vector Bemisia tabaci (Gennadius)

The transovarial transmission of two species of begomovirus, Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV), through generations of Bemisia tabaci of the B and Q biotypes has been investigated. Different life stages of the progeny of viruliferous female whiteflies have been analysed by PCR detection of viral DNA and infectivity tests. Our results indicate that TYLCSV DNA can be detected in eggs and nymphs, and to a lesser extent adults, of the first-generation progeny. Infectivity tests using a large number of adult progeny of the first, second, and third generation indicate that even when viral DNA is inherited, infectivity is not. For TYLCV, neither viral DNA nor infectivity were associated with the progeny of viruliferous female whiteflies. Because the inherited viral DNA is unable to give rise to infections, the transovarial transmission of TYLCSV DNA appears to have no epidemiological relevance.     

Diversity of genomic breakpoints in TFG-ALK translocations in anaplastic large cell lymphomas: identification of a new TFG-ALK(XL) chimeric gene with transforming activity

Anaplastic large cell lymphomas are associated with chromosomal aberrations involving the anaplastic lymphoma kinase (ALK) gene at 2p23 that result in the expression of novel chimeric ALK proteins with transforming properties. In most of these tumors, the t(2;5)(p23;q35) generates the NPM-ALK fusion gene. However, several studies have now demonstrated that genes other than NPM may be fused to the ALK gene. We have recently described two different ALK rearrangements involving the TRK-fused gene (TFG) in which the same portion of ALK was fused to different length fragments of the 5' TFG region. These two rearrangements encoded chimeric proteins of 85 kd (TFG-ALK(S)) and 97 kd (TFG-ALK(L)), respectively. In this study, we have identified a new ALK rearrangement in which the catalytic domain of ALK was fused to a larger fragment of the TFG gene (TFG-ALK(XL)), encoding for a fusion protein of 113 kd. Genomic analysis of these three TFG-ALK rearrangements revealed that the TFG breakpoints occur at introns 3, 4, and 5, respectively, whereas the ALK breakpoints always occur in the same intron. No homologous regions or known recombination sequences were found in these regions. Transfection experiments using NIH-3T3 fibroblasts showed a similar transforming efficiency of TFG-ALK variants compared with NPM-ALK. In addition, in common with NPM-ALK, the TFG-ALK proteins formed stable complexes with the signaling proteins Grb2, Shc, and PLC-gamma. In conclusion, these findings indicate that the TFG may use a variety of intronic breakpoints in ALK rearrangements generating fusion proteins of different molecular weights, but with similar transforming potential than NPM-ALK.     

Interaction between rod and cone systems in dichoptic visual masking

The brightness of a brief flash of light is reduced by the suitable presentation of a second flash in an adjacent region of the visual field. This making effect (metacontrast) can be induced dichoptically, that is with the test flash presented to one eye and the masking flash to the other. By a suitable choice of wavelengths and conditioning field, the test flash may be arranged to effectively stimulate only rod receptors and the masking flash only cone receptor. A dichoptic masking effect is still obtained.     

Transmission of a spotted fever group rickettsia by Amblyomma hebraeum (Acari: Ixodidae)

Amblyomma hebraeum, a cattle tick common in southern Africa, was demonstrated to be capable of maintaining an infection with an unclassified spotted fever group rickettsia both transtadially and transovarially. All feeding stages of the tick transmitted the infection to rabbits. The rickettsia was isolated and found to be serotypically distinct from three strains of Rickettsia conorii by microimmunofluorescence. Rabbit serum titers were found to be higher with indirect fluorescent antibody (IFA) tests using the Amblyomma isolate than with those using a commercially available IFA test for R. conorii.     

Effect of orally administered monoclonal antibody on persistent Cryptosporidium parvum infection in scid mice.

Scid mice, persistently infected after exposure to 10(7) Cryptosporidium parvum oocysts, were treated daily for 14 to 17 days with 0.4 mg of monoclonal antibody (mAb) 17.41 administered by the oral route. Mice receiving mAb 17.41 shed significantly fewer (P < 0.005) C. parvum oocysts than scid mice receiving isotype control mAb. Intestinal (but not gastric) infectivity scores were also reduced for scid mice treated with mAb 17.41 (P < 0.01).     

Effect of spleen cell populations on resolution of Cryptosporidium parvum infection in SCID mice.

Persistent infection was established in SCID mice given 10(7) Cryptosporidium parvum oocysts. Nine groups of infected SCID mice were inoculated with 10(6), 10(5), or 10(4) total spleen cells, CD8-depleted spleen cells, or CD4-depleted spleen cells from naive BALB/c donors. Infection was significantly reduced in all treatment groups. The most profound effect occurred with spleen cell preparations containing CD4 T lymphocytes but depleted of CD8 T lymphocytes.     

Preferential localisation of human lymphocytes bearing gamma delta T cell receptors to the red pulp of the spleen.

About 4% of human T cells carry antigen receptor composed of gamma and delta chains (rather than alpha and beta chains). Double immunoenzymatic staining of frozen sections of 14 samples of human spleen showed that gamma delta bearing T cells were preferentially localised in the red pulp of this organ where on average they accounted for 17% of all T cells. There was no correlation between the number of gamma delta T cells and the diagnosis, with the exception of a case of malaria in which an unusually high number (40%) of T cells were of this type. The gamma delta bearing T cells were scattered randomly through the red pulp, and double staining combined with a marker of splenic sinusoids (CD36) showed that almost all lie outside the sinusoids within the cords of the red pulp. It is suggested that the double immunoenzymatic technique could be used for further studies of the prevalence of gamma delta bearing T cells in lymphocytic infiltrates.