Characteristics of cultured tomato cells after prolonged exposure to medium containing polyethylene glycol

Cell lines of tomato (Lycopersicon esculentum Mill., cv. VFNT-Cherry) have been isolated, which are capable of growing in media containing polyethylene glycol (PEG) 6000 with water potentials as low as −15 or −22 bar. After prolonged exposure to media containing PEG, these cell populations have reduced abilities to grow in the absence of PEG. Upon resuspension in PEG-free medium, the cells swell and begin to release metabolites, including protein. Measurement by plasmometry of the osmotic potential of cells selected in medium with −22 bar water potential indicates that they maintain, at the end of the growth cycle, an osmotic potential of approximately −26 bar. This is compared to an osmotic potential of −9 bar for nonselected cells in medium without PEG, having an initial water potential of −4 bar. Thus, considerable osmotic adjustment occurs as a result of exposure to external low water potential. The results also indicate that PEG does not contribute significantly to osmotic adjustment of the cells.     

The prevalence of 'Candidatus Arsenophonus phytopathogenicus' infecting the planthopper Pentastiridius leporinus (Hemiptera: Cixiidae) increase nonlinearly with the population abundance in sugar beet fields

The planthopper Pentastiridius leporinus (L.) (Hemiptera: Cixiidae) has been identified as the main vector of 'Candidatus Arsenophonus phytopathogenicus', a plant pathogenic bacterium associated to a sugar beet disease in eastern France called syndrome 'basses richesses'. In a 2-yr survey (2006-07), we quantified the abundance of P. leporinus populations migrating into 29 sugar beet fields in eastern France. Sticky traps posted in these fields were monitored on a twice-weekly (2006) or weekly (2007) basis. Subsets of the captured planthoppers were tested for the presence of Ca. A. phytopathogenicus through polymerase chain reaction (PCR). Our results showed that planthoppers colonized sugar beet fields in June and July of each year, following temporal patterns of migration that were fitted to logistic functions. The number of planthoppers migrating into sugar beet fields greatly varied among the fields and the years surveyed, averaging from a few (2-10) to over 400 planthoppers per trap. Interestingly, the prevalence of planthoppers infected by Ca. A. phytopathogenicus increased nonlinearly with the abundance of planthoppers captured on the traps. The proportion of infection for Ca. A. phytopathogenicus ranged from ?0.07-1 (total infection) in small (2-10 planthoppers per trap) and large (400 planthoppers per trap) populations, respectively. We hypothesize that the outbreaks of P. leporinus in sugar beet fields, and the consequent increased rates of planthoppers infected by the Ca. A. phytopathogenicus, are key factors leading to the emergence of the sugar beet disease in eastern France.     

Selective Augmentation of Stem Cell Populations in Structural Fat Grafts for Maxillofacial Surgery

Structural fat grafting utilizes the centrifugation of liposuction aspirates to create a graded density of adipose tissue. This study was performed to qualitatively investigate the effects of centrifugation on stem cells present in adipose tissue. Liposuction aspirates were obtained from healthy donors and either not centrifuged or centrifuged at 1,800 rpm for 3 minutes. The obtained fat volumes were divided into three layers and then analyzed. The results demonstrate that centrifugation induces a different distribution of stem cells in the three layers. The high-density layer displays the highest expression of mesenchymal stem cell and endothelial markers. The low-density layer exhibits an enrichment of multipotent stem cells. We conclude that appropriate centrifugation concentrates stem cells. This finding may influence the clinical practice of liposuction aspirate centrifugation and enhance graft uptake.     

Why babies look like their daddies: paternity uncertainty and the evolution of self-deception in evaluating family resemblance

It has been suggested that in a socially monogamous system where fathers invest in their mate's offspring but paternity is far from certain, it will be adaptive on the part of infants to conceal their father's identity; but the opposite claim has also been made that this is against the genetic interests of the fathers, and a high frequency of adulterine births will select instead for paternal resemblance. In this article, I present a simple theoretical model that suggests that neonatal anonymity benefits fathers, mothers, and children. Once anonymity becomes established, however, all babies start paying the cost of paternity uncertainty, that is, the reduction in paternal care due to fathers not knowing whether they have truly sired their mate's offspring. By diminishing the fitness of babies, such a cost bounces back as lowered fitness for parents as well. We should then expect the evolution of maternal strategies directed to decrease paternity uncertainty, in the form of instinctive and unsolicited comments on babies' resemblance to their putative fathers. In contradiction to the widespread belief that it would be in fathers' interest to be skeptical of these allegations, the model suggests that, under conditions of infant anonymity, fathers will actually promote their own fitness by believing their spouses. Received in revised form: 5 September 2001 Electronic Publication