Mapping and characterization of new EST-derived microsatellites for potato (Solanum tuberosum L.).

Microsatellites, or simple sequence repeats (SSRs) are very useful molecular markers for a number of plant species. They are commonly used in cultivar identification, plant variety protection, as anchor markers in genetic mapping, and in marker-assisted breeding. Early development of SSRs was hampered by the high cost of library screening and clone sequencing. Currently, large public SSR datasets exist for many crop species, but the number of publicly available, mapped SSRs for potato is relatively low (approximately 100). We have utilized a database mining approach to identify SSR-containing sequences in The Institute For Genomic Research Potato Gene Index database (http://www.tigr.org), focusing on sequences with size polymorphisms present in this dataset. Ninety-four primer pairs flanking SSR sequences were synthesized and used to amplify potato DNA. This study rendered 61 useful SSRs that were located in pre-existing genetic maps, fingerprinted in a set of 30 cultivars from South America, North America, and Europe or a combination thereof. The high proportion of success (65%) of expressed sequence tag-derived SSRs obtained in this work validates the use of transcribed sequences as a source of markers. These markers will be useful for genetic mapping, taxonomic studies, marker-assisted selection, and cultivar identification.

Improved response of a murine fibrosarcoma (Meth-A) to interstitial radiation when combined with hyperthermia.

Removable Iridium-192 implants provided a dose of 10 Gy/day or 41.5 cGy/hr at 0.5 cm from the center of 1.0 cm diameter tumors. The total radiation (x) alone was 20, 40 or 60 Gy, representing 2, 4, or 6 days of continuous radiation. The doses used for the combined treatments at elevated temperatures were 10, 20 or 30 Gy. The local tumor hyperthermia (LTH) treatment (43.6 for 35 min, water bath) was administered once for each 10 Gy of dose. The combined radiation + LTH was clearly superior to that achieved with radiation or LTH alone and yielded Thermal Enhancement Ratios (TER) of 3.4-3.9. Local tumor control rate was 67% and 89% for the 20 and 30 Gy x + LTH groups, respectively. A comparison of the results obtained in this study with those of earlier studies on the same tumor system indicate that the effects of Iridium-192 alone on this rapidly proliferating tumor were comparable to similar total doses of fractionated external beam radiation. Iridium + LTH produced a tumor response comparable to that achieved with external fractionated radiation + LTH. Combined treatment effect of elevated temperature appears to be less dose rate dependent in the range of 40 cGy/hr to 100 cGy/min and more dependent upon total dose accumulation.

Role of placenta in maternal-fetal vitamin transfer in humans.

Vitamins B12, B6, biotin, folate, thiamine, riboflavin, pantothenate, and nicotinate were determined in maternal and fetal blood and placental tissue of normovitaminemic and hypovitaminemic mothers who disclaimed supplemental vitamin intake during pregnancy. No biotin or pantothenate deficits were observed in the gravidas. Hypovitaminemic mothers transferred less B12, folate, and B6 to the fetus and placenta than normovitaminemic mothers. Vitamins given by mouth increased maternal fetal, and placental levels of folate, but B6 increased only in maternal blood and the placenta; biotin and pantothenate increased only in fetal blood. Except for riboflavin, nicotinate, and pantothenate, the intramuscular administration of vitamins increased the levels of other vitamins in maternal and fetal blood and placental tissue. Results suggest that the placenta stores vitamins and the tissue vitamin receptors must be saturated before adequate transfer of vitamins to the fetus occurs.