The virus-vector relationship of the tomato leafcurl virus (TLCV) and its vector,Bemisia tabaci gennadius (Hemiptera: aleyrodidae)

Basic studies carried out in India showed that the incubation period of TLCV in plants varied from 8 days in August to 90 days in winter. The acquisition threshold for the whitefly,Bemisia tabaci Gen., was 31 min; it resulted in 3% transmission. An acquisition access of 24 h for a female whitefly on a TLCV source resulted in 30% transmission. A minimum feeding period of 32 min was required by a viruliferous whitefly to cause infection on tomato test plants; this gave 4% transmission. With inoculation access of 24 h on tomato test plants, the transmission rose to 24%. Starving the vector for 1 h pre-acquisition or 1 h pre-inoculation resulted in higher levels of transmission of TLCV: 36 and 40%, respectively, compared with 20% for non-starved whiteflies. Extending the fasting period beyond 1 h resulted in a reduced transmission level. The whiteflies could acquire the virus from the cotyledonary leaves of an infected tomato plant, with a resultant 28% transmission; but infection did not occur when the whiteflies had an inoculation access to such leaves. Higher transmission rates were obtained when the younger leaves on tomato plants were used for acquisition and inoculation. Transmission was 8 and 38% when five whiteflies per plant were allowed 24 h of acquisition access to 11- and 2-month-old virus sources, respectively. After an acquisition access of 24 h to a TLCV source, male and female whiteflies retained their infectivity for 5 and 53 days, respectively. Nymphs can acquire and transmit the virus. When ten whiteflies of each sex were given 24 h of acquisition and of inoculation access, the subsequent transmission rate of males and females was 56 and 86%, respectively. This virus is not transovarially transmitted. Whitefly colonies raised on brinjal were more efficient (70 and 84% transmission in two experiments) than those raised on chilli, cotton, cowpea, tobacco or tomato.     

A new pattern of morphofunctional relationship among cranial nerves: Evidence of anatomical and physiological connection between trigeminus and oculomotor nerves

It is shown that the cell bodies of the afferent fibres supplying the proprioceptivity to the extrinsic eye muscles are located within the semilunar ganglion. Furthermore, some Gasserian cells have central processes which enter the midbrain through the oculomotor nerve. Sensory ganglion cells, derived from the same strand of placodal cells forming the ophthalmic lobe, can be constantly detected within the oculomotor nerve of ox, monkey and man.

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Kurzfassung Unsere Forschungen haben ergeben, dass sich die Zellkörper der fibrae afferentes, die dem äusserlichen Augenmuskeln die propriozeptive Sensibilität geben, im Ganglion des Gasser befinden. Ausserdem haben einige Zellen des Gasserschenganglion zentrale Verzweigungen die durch den Nervus oculomotorius in den Hirnstamm führen. Sensitive Ganglionzellen, die von der gleichen Reihe plakodischer Zellen stammen, und den lobus oftalmicus Gasseri formen, sind regelmassig im nervus oculomotorius des Rindes, des Affen und des Menschen zu finden.

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Resume Nos recherches ont démontré que, chez le Mouton et le Porc, le ganglion de Gasser contient les corps cellulaires des fibres nerveuses desservant les fuseaux neuromusculaires des muscles extrinsèques de l'oeil. En outre, quelques cellules du ganglion de Gasser ont leurs prolongements centraux qui se portent au tronc cérébral en suivant à rebours les radicules du nerf oculomoteur. En fin, on a trouvé constamment des cellules ganglionnaires sensitives dans l'oculomoteur du Boeuf, du Singe et de l'Homme; ces cellules proviennent du même cordon de cellules placodiales qui forme le lobe ophthalmique du ganglion semilunaire.

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Riassunto Le nostre ricerche hanno dimostrato che i corpi cellulari delle fibre nervose afferenti, che danno la sensibilità propriocettica al muscolo oculare estrinseco, si trovano nel ganglione di Gasser. Inoltre, alcune cellule del ganglione di Gasser hanno diramazioni centrali che portano al tronco cerebrale attraverso il nervo oculomotore. Infine, si sono costantemente incontrati nel nervo oculomotore del bovino, della scimmia e dell'uomo, cellule sensitive che provengono dallo stessotronco di cellule placodali che formano il lobo oftalmico.

     

A light and scanning-electron microscopic study of infection of tomato plants by virulent and avirulent races of Cladosporium fulvum

Infection of tomato plants byCladosporium fulvum Cooke was studied using light and scanning-electron microscopy. Races 1.2.3 and 4 ofCladosporium fulvum were used, whereas tomato cultivars, carrying the Cf2 gene (susceptible to race 1.2.3 and immune to race 4) and the Cf4 gene (immune to race 1.2.3 and susceptible to race 4) served as differentials. No differences were observed in growth between compatible and incompatible combinations during germination, subsequent formation of runner hyphae and stomatal penetration. Runner hyphae did not show directional growth towards stomata. Penetration usually occurred on the third or fourth day after inoculation. In compatible combinations the fungus grew intercellularly, often in close contact with spongy mesophyll cells. Under optimal conditions it did not cause visible damage to plant cells during early stages of infection. Under suboptimal conditions in winter, the host cells often reacted with callose deposition, but growth of the fungus did not appear to be inhibited. Ten to twelve days after inoculation conidiophores emerged through the stomata and produced conidia. In incompatible combinations fungal growth was arrested one to two days after penetration and confined to stomata and surrounding cells. Very soon the host cells, in contact with the fungus, deposited extensive amounts of callose. Later these cells turned brown and collapsed. At the surface of the host cells, contacted by fungal hyphae, abundant extracellular material could be observed by scanning-electron microscopy. Removing the epidermis of leaves before inoculation delayed the resistant response. On stripped leaves the rate of fungal growth was equal for both interactions up to ten days after inoculation, but the incompatible combination lacked sporulation.     

Variation of canine and feline frontal-plane QRS axes with lead choice and augmentation ratio

The intraindividual variability in mean electric axis referable to choice of ECG leads and augmentation ratio was investigated by means of a digital computer program. Although, in theory, the choice of leads for determining the QRS axis should make no difference, the maximum intraindividual variation in axis angle was about 50 degrees for canine and feline subjects. The angle conputed for the lead combinations I and III and I and aVF will usually fall within 5 to 10 degrees of the mean of all lead combinations, but larger variations are seen at time. The application of an "augmentation ratio" for the augmented unipolar leads was most helpful when it was individually computed. Further methods of lead-vector improvement are discussed.     

Alternative complement pathway in bovine serum: lysis of human erythrocytes.

The hemolysis of unsensitized human erythrocytes by fresh bovine serums was investigated. Lysis occurred in ethylene glycol bis-amino tetraacetate buffers and with serums depleted of Clq. Serums extensively absorbed with packed human erythrocytes at 0 C effectively lysed human erythrocytes, but optimal lytic capacity required target cells "sensitized" with a heat-stable serum factor. Lysis did not occur with serums absorbed with zymosan at 17 C or heat inactivated at 50 C. These results indicate that human erythrocytes can activate the alternative pathway of complement in bovine serums. Lysis can proceed in the apparent absence of antibodies, although their presence may enhance the reaction.