Immunity to K1 killer toxin: internal TOK1 blockade.

K1 killer strains of Saccharomyces cerevisiae harbor RNA viruses that mediate secretion of K1, a protein toxin that kills virus-free cells. Recently, external K1 toxin was shown to directly activate TOK1 channels in the plasma membranes of sensitive yeast cells, leading to excess potassium flux and cell death. Here, a mechanism by which killer cells resist their own toxin is shown: internal toxin inhibits TOK1 channels and suppresses activation by external toxin

A molecular target for viral killer toxin: TOK1 potassium channels.

Killer strains of S. cerevisiae harbor double-stranded RNA viruses and secrete protein toxins that kill virus-free cells. The K1 killer toxin acts on sensitive yeast cells to perturb potassium homeostasis and cause cell death. Here, the toxin is shown to activate the plasma membrane potassium channel of S. cerevisiae, TOK1. Genetic deletion of TOK1 confers toxin resistance; overexpression increases susceptibility. Cells expressing TOK1 exhibit toxin-induced potassium flux; those without the gene do not. K1 toxin acts in the absence of other viral or yeast products: toxin synthesized from a cDNA increases open probability of single TOK1 channels (via reversible destabilization of closed states) whether channels are studied in yeast cells or X. laevis oocytes

Cytolethal distending toxin (CDT)-negative Campylobacter jejuni strains and anti-CDT neutralising antibodies induced during human infection but not chicken colonisation

The cytolethal distending toxin (CDT) of Campylobacter jejuni was detectable, using an in vitro assay, in most but not all of 24 strains tested. The reason for the absence of toxin activity in these naturally occurring CDT-negative C. jejuni strains was then investigated at the genetic level. CDT is encoded by three highly conserved genes, cdtA, -B, and -C. In the CDT-negative strains, two types of mutation were identified. The CDT activities of C. jejuni strains possessing both types of mutation were successfully complemented with the functional genes of C. jejuni 11168. The first type of mutation comprised a 667-bp deletion across cdtA and cdtB and considerable degeneration in the remainder of the cdt locus. Using a PCR technique to screen for this deletion, this mutation occurred in fewer than 3% of 147 human, veterinary, and environmental strains tested. The second type of mutation involved at least four nonsynonymous nucleotide changes, but only the replacement of proline with serine at CdtB position 95 was considered important for CDT activity. This was confirmed by site-directed mutagenesis. This type of mutation also occurred in fewer than 3% of strains as determined using a LightCycler biprobe assay. The detection of two CDT-negative clinical isolates raised questions about the role of CDT in some cases of human campylobacteriosis. To determine if anti-CDT antibodies are produced in human infection, a toxin neutralization assay was developed and validated using rabbit antisera. Pooled human sera from infected patients neutralized the toxin, indicating expression and immunogenicity during infection. However, no neutralizing antibodies were detected in colonized chickens despite the expression of CDT in the avian gut as indicated by reverse transcription-PCR

Evaluation de la teneur en iode des sels de cuisine dans les ménages de deux zones d’endémie goitreuse du Bénin

La consommation régulière de sel adéquatement iodé est indispensable dans la prévention et la lutte contre les troubles dus à la carence en iode (TDCI). L’objectif de ce travail était d’évaluer la teneur en iode des sels de cuisine dans deux zones (départements du Borgou et des Collines) d’endémie goitreuse du Bénin. Du 15 avril au 15 septembre 2010, 327 échantillons de sels de cuisine ont été collectés dans les ménages de quatre communes de ces deux zones par un échantillonnage stratifié et aléatoire. La teneur en iode des échantillons de sels a été déterminée quantitativement par la méthode du titrage iodométrique et qualitativement avec le kit MBI. Par la technique du titrage iodométrique, la teneur moyenne en iode des sels de cuisine était de 33,836 ± 17,046 ppm ; 86,24% des échantillons de sels avaient une teneur en iode supérieure ou égale à 15 ppm, 11,31% avaient moins de 15 ppm et 2,45% avaient 0 ppm. Avec le kit MBI, 90,83% des échantillons de sels avaient plus de 15 ppm d’iode, 3,97% avaient moins de 15 ppm d’iode et 5,20% avaient 0 ppm d’iode. Conformément à la norme recommandée (15 à 40 ppm), 54,74% des échantillons de sels étaient correctement iodés. Les échantillons de sels de cuisine consommés par les ménages des départements du Borgou et des Collines ne sont pas adéquatement iodés. Des efforts restent encore à faire pour atteindre les objectifs de l’OMS sur l’iodation universelle du sel dans ces deux départements.Keywords: Iodation, titrage iodométrique, MBI, TDC

Late-season nitrogen applications in high-latitude strawberry nurseries improve transplant production pattern in warm regions

The influence of late-season nitrogen (N) applications on the fruiting pattern of strawberry runner plants of ‘Camarosa’ was determined over three growing seasons. Experiments were carried out in highlatitude nurseries in northern California and fruit production trials were established in southern California. A total of 80 kg/ha of foliar nitrogen was delivered in three applications to the nursery in late summer. Late-season foliar nitrogen applications: (1) increased early yields (+22% on average) as well as the number of early marketable fruit, (2) did not affect total season yields, fruit size, appearance and firmness and (3) resulted in greater N concentration in leaves, crowns and roots. Runner plants with leaf N concentration within the sufficiency range (1.9 - 2.8% of dry mass) produced the highest early yields. Total nonstructural carbohydrate concentrations decreased in most of the N-treated plants. Apparently, nursery late-season foliar nitrogen applications enhance N mobilization to crown and root, stimulate plant activity during the period of flower differentiation after planting, accelerating flower development and contributing to the advancement of fruit production

Determinants of Referral Practices of Clients by Traditional Birth Attendants in Ilorin, Nigeria

A sizeable number of deliveries still take place with the assistance of Traditional Birth Attendants in Nigeria. This study aims to determine the factors that determine the referral practices of the TBAs in Ilorin of high risk and complicated pregnancies. This descriptive study was conducted among all the 162 registered TBAs in Ilorin that were traceable using pre-tested semi-structured interviewer-administered questionnaire. About 90%, whose source of skill acquisition was by inheritance did not refer their clients appropriately compared with 48% of those whose source of skill acquisition was through formal training (p<0.05). The more the numbers of trainings, the more appropriate the referral (p<0.05). Having supervisory visit by qualified personnel is associated with appropriate referral practices (p<0.05). Regular training and re-training of TBAs with routine monitoring and supportive supervision will promote prompt referral of high risk and complicated pregnancies and deliveries (Afr. J. Reprod. Health 2010; 14[2]:77-84)