Advances in alternative DNA delivery techniques

This review describes recent advances in alternative DNA-delivery techniques with particular emphasis on silicon carbide fibers, intact tissue electroporation, electrophoresis and microinjection. The advantages/disadvantages of each method along with a historical overview and theory of practice are discussed.     

Tampering with cancer chemoresistance by targeting the TGM2-IL6-autophagy regulatory network

Macroautophagy/autophagy is a well-established process involved in maintaining cellular homeostasis, but its role in cancer is complex and even controversial. Many studies have reported a correlative relationship between increased autophagy and evolving cancer cells under stress conditions such as nutrient or oxygen deprivation; however, there has been a lack of a plausible mechanistic link to properly target the autophagy process in the context of this microenvironment. We recently unveiled a positive regulatory loop involving TGM2 (transglutaminase 2)-NFKB/NF-κB signaling, IL6 and autophagy in cancer using mantle cell lymphoma (MCL) as a model system. These pathways are functionally connected to each other, thereby promoting malignant B cell survival and leading to enhanced lymphoma progression both in mice and in patients. Disruption of this network could provide an opportunity to increase the efficacies of current therapies and to reduce MCL drug resistance.     

Dual role of osteoblastic proenkephalin derived peptides in skeletal tissues

Proenkephalin encodes a group of small peptides with opiate-like activity, the endogenous opioids, known to function as neurohormones, neuromodulators, and neurotransmitters. Recently, we have demonstrated that in addition to its abundance in fetal brain tissue, proenkephalin is highly expressed in nondifferentiated mesodermal cells of developing fetuses. We identified the skeletal tissues, bone, and cartilage as major sites of proenkephalin expression. To examine the possibility that proenkephalin is involved in bone development we have studied the expression of this gene in bone-derived cells, its modulation by bone active hormones, and the effects of enkephalin-derived peptides on osteoblastic phenotype. Our studies revealed that osteoblastic cells synthesize high levels of proenkephalin mRNA which are translated, and the derived peptides are secreted. Reciprocal interrelationships between osteoblast maturation and proenkephalin expression were established. These results together with our observations demonstrating inhibitory effects of proenkephalin-derived peptides on osteoblastic alkaline phosphatase activity, strongly support the notion that proenkephalin is involved in bone development. A different direction of research by other investigators has established the capability of the opioid system in the periphery to participate in the control of pain. On the basis of these two lines of observation, we would like to present the following hypothesis: The potential of embryonic skeletal tissue to synthesize proenkephalin-derived peptides is retained in the adult in small defined undifferentiated cell populations. This potential is realized in certain situations requiring rapid growth, such as remodeling or fracture repair. We suggest that in these processes, similarly to the situation in the embryo, the undifferentiated dividing cells produce the endogenous opioids. In the adult these peptides may have a dual function, namely participating in the control of tissue regeneration and in the control of pain. © 1994 Wiley-Liss, Inc.     

The effects of culture medium rigidity on adventitious bud production and tissue vitrification in needle cultures of Sitka spruce [Picea sitchensis (Bong.) Carr.]

Adventitious bud formation on Sitka spruce [ Picca sitchensis (Bong.) Carr.] needle explants was strongly dependent upon the rigidity of the culture medium. In general, of organogenesis was greatest on weak gels and poorest on more rigid gels resulting from increased medium pH or agar strength. There was a significant interaction between agar strength and pH, with the optimum pH for organogenesis declining with increasing agar strength. Poor organogenesis at high agar concentrations was not due to toxic impurities since increased adventitious bud production could be stimulated by decreasing the medium pH whilst maintaining a high agar strength and an agar washing treatment had no significant effect. Although high levels of organogenesis could be sustained on weak gels the resultant adventitious shoots often showed severe vitrification. The frequency of shoots showing vitrification could be reduced by growing the tissues on harder media but this resulted in reduced shoot elongation. Vitrification of needle tissues did not stimulate the formation of adventitious buds in the absence of cytokinins.     

Estimating survival of the shortfin mako Isurus oxyrinchus (Rafinesque) in the north-west Atlantic from tag-recapture data

Survival was estimated for shortfin mako Isurus oxyrinchus in the north-west Atlantic from tag-recapture data. The data used in this study were collected by the National Marine Fisheries Service Cooperative Shark Tagging Programme from 1962 to 2003. In total, 6309 shortfin mako sharks were tagged, of which 730 were recaptured. The high recapture rate of 11·6% for this species provided adequate recapture data to carry out survival analyses. Estimates of survival were generated with the computer software MARK, which provided a means for estimating parameters from tagged animals when they were recaptured. The results of several models are presented with various combinations of constant and time-specific survival and recovery rates. A parametric bootstrap and the median variance inflation factor ( ) approach were used to test the fit of the general model to the data. The estimated indicated a very good model fit. The models with time invariant survival rate had the most support from the data and no group or time period effects were found. Recovery rate ( f ) appeared to increase from 0·043 in the early years to 0·056 in the later years. The nominal survival rate of 0·59 year⁻¹ was adjusted with an estimated tag-shedding rate of 0·26 year⁻¹ to generate a final corrected annual survival estimate of 0·79 with a 95% CI of 0·71–0·87.     

Structural and metabolic properties of green tissue cultures from a CAM plant, Kalanchoë blossfeldiana hybr. Montezuma

Abstract Crassulacean acid metabolism (CAM) was studied in mixotrophic callus tissue cultures of Kalanchoë blossfeldiana hybr. Montezuma and compared with plants propagated from the calli. The ultrastructural properties of the green callus cells are similar to mesophyll cells of CAM plants except that occasionally abnormal mitochondria were observed. There was permanent net CO₂ output by the calli in light and darkness, which was lower in darkness than in light. The calli exhibited a diurnal rhythm of malic acid, with accumulation during the night and depletion during the day. ¹⁴C previously incorporated by dark CO₂ fixation into malate was transferred upon subsequent illumination into end products of photosynthesis. All these data indicate that CAM operates in the calli tissue. The results revealed that the capacity for CAM is obviously lower in the calli compared with plantlets developing from the calli, or with ‘adult’ plants. The data suggest also that CAM in the calli was not limited by the activities of CAM enzymes.