all-trans-retinoic acid preserves viability of fibroblasts and keratinocytes in full-thickness human skin and fibroblasts in isolated dermis in organ culture

Human dermal fibroblast and human epidermal keratinocyte survival was examined under various conditions in organ culture. Using cell recovery from organ-cultured tissue as the criterion, it was observed that no keratinocytes and few fibroblasts survived incubation for 10-12 days in serum-free basal medium containing a low level (0.15 mM) of extracellular Ca2+. Increasing the extracellular Ca2+ concentration to 1.4 mM or treating the tissue with 3 microM retinoic acid (RA) under low Ca2+ conditions resulted in increased keratinocyte and fibroblast survival; the two treatments together were more effective than either treatment alone. The same treatments preserved fibroblast survival when pieces of isolated dermal tissue were incubated in organ culture and also supported fibroblast survival in monolayer culture. These findings indicate that recovery of keratinocytes and fibroblasts from skin after maintenance in organ culture provides a simple but definitive measure of the viability of the major cellular elements present in the tissue. These findings suggest that RA treatment enhances survival of both fibroblasts and keratinocytes and that these effects of RA can be seen at physiological Ca2+ concentrations as well as at suboptimal levels of extracellular Ca2+. Finally, these results indicate that the dermis is a direct target of RA.     

Vertebral artery injury during anterior decompression of the cervical spine. A retrospective review of ten patients

Ten patients who suffered iatrogenic injury to a vertebral artery during anterior cervical decompression were reviewed to assess the mechanisms of injury, their operative management, and the subsequent outcome. All had been undergoing a partial vertebral body resection for spondylitic radiculopathy or myelopathy (4), tumour (2), ossification of the posterior longitudinal ligament (1), nonunion of a fracture (2), or osteomyelitis (1). The use of an air drill had been responsible for most injuries. The final control of haemorrhage had been by tamponade (3), direct exposure and electrocoagulation (1), transosseous suture (2), open suture (1), or open placement of a haemostatic clip (3). Five patients had postoperative neurological deficits, but most of them resolved. We found direct arterial exposure and control to be safe, quick and reliable. Careful use of the air drill, particularly in pathologically weakened bone, as in infection or tumour, is essential. Arterial injury is best avoided by a thorough knowledge of the anatomical relationships of the artery, the spinal canal, and the vertebral body.     

The 73-kb pIAA plasmid increases competitive fitness of Pseudomonas syringae subspecies savastanoi in oleander

Pseudomonas syringae subsp. savastanoi causes tumors on olive and oleander by producing the plant growth regulators indoleacetic acid (IAA) and cytokinins following infection of the plant. The contribution of IAA production to the ability of P. syringae subsp. savastanoi to grow and survive in oleander leaf tissue was studied. Bacterial strains differing only with respect to IAA production were characterized. Growth and survival of wild-type and two mutant strains of P. syringae subsp. savastanoi in oleander leaf tissue were monitored by weekly colony counts and IAA plate assays. Growth rate of the three strains in culture and in planta did not differ significantly. However, the wild-type strain reached a higher population density and maintained its maximum density at least 9 weeks longer than either mutant population. An insertion mutant containing the IAA plasmid (pIAA), but incapable of IAA production, did not maintain a higher population density than a strain cured of the IAA plasmid. The pIAA-cured strain maintained a higher population density when coinoculated with an IAA-producing strain than when inoculated alone. These results suggest that IAA production may contribute to the fitness of P. syringae subsp. savastanoi in oleander tissue and that the iaa operon alone may be responsible for the competitive advantage of cells harboring pIAA.     

Confidence intervals for a binomial proportion

Thirteen methods for computing binomial confidence intervals are compared based on their coverage properties, widths and errors relative to exact limits. The use of the standard textbook method, x/n +/- 1.96 square root of [(x/n)(1-x/n)/n], or its continuity corrected version, is strongly discouraged. A commonly cited rule of thumb stating that alternatives to exact methods may be used when the estimated proportion p is such that np and n(1(-)p) both exceed 5 does not ensure adequate accuracy. Score limits are easily calculated from closed form solutions to quadratic equations and can be used at all times. Based on coverage functions, the continuity corrected score method is recommended over exact methods. Its conservative nature should be kept in mind, as should the wider fluctuation of actual coverage that accompanies omission of the continuity correction.