To study gene mutations in different organs and tissues of an experimental animal, we produced transgenic mice harboring bacteriophage lambda shuttle vectors integrated in the genome in a head-to-tail arrangement. As a target for mutagenesis, the selectable bacterial lacZ gene was cloned in the vector. The integrated vectors were rescued from total genomic DNA with high efficiency by in vitro packaging and propagation of the phages in a LacZ- strain of Escherichia coli C. The background mutation frequencies in brain and liver DNA appeared to be low, as was indicated by the absence of colorless plaques among 138,816 and 168,160 phage isolated from brain and liver DNA, respectively. Treatment of adult female transgenic mice with N-ethyl-N-nitrosourea resulted in a dose-dependent increase of the frequency of mutated vectors isolated from brain DNA, up to 7.4 x 10(-5) at 250 mg of the alkylating agent per kilogram of body weight. At this dose, in liver DNA of the same mice, mutation frequencies were approximately 3 x 10(-5). DNA sequence analysis of four mutant vectors isolated from brain DNA indicated predominantly G.C----A.T transitions. These results demonstrate the value of this transgenic mouse model in studying gene mutations in vivo. In addition to its use in fundamental research, the system could be used as a sensitive, organ-specific, short-term mutagenicity assay.
Background Looking to further reduce the operative trauma of laparoscopic cholecystectomy, we developed, in patients with no history of cholecystitis and a normal BMI, a scarless operation through the umbilicus. The operative technique, along with the results of the first 10 patients operated in this way, are fully described. Methods 10 female patients underwent transumbilical scarless laparoscopic cholecystectomy. Through the umbilicus, two trocars of 5 mm were introduced parallel to another with a bridge of fascia between them (one for the 5-mm laparoscope and the other for the grasper). With the help of one 1-mm Kirschner wire, introduced at the subcostal line and bent with a special designed device, the gallbladder was pulled up and the triangle of Callot was dissected free, clipped, cut, and the gallbladder was subsequently resected. Finally the gallbladder was taken out through the umbilicus and the umbilicus reconstructed. Results 10 female patients, mean age 36 years (range: 31-49), mean body mass index (BMI) 23 (range: 20-26), after one attack (six patients) or a second attack (four patients) and cholelithiasis confirmed by ultrasonography with no suspicion of inflammation were included in this preliminary study. Mean operative time was 70 minutes (range: 65-85) with no conversions; hospital stay was less than 24 hours with no complications. Conclusion Looking to reduce operative trauma and improve the cosmetic result following laparoscopic cholecystectomy, a transumbilical operative technique has been developed. Results of the operative procedure in a selected group of patients are encouraging with no signs of inflammation and normal BMI. The umbilicus can be developed as a natural port for performing various operative procedures with the help of the traction produced by thin Kirschner wires.
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