Rat synapsin 1 promoter mediated transgene expression in testicular cell types.

Previous reports described the rat synapsin 1 promoter as primarily neuron selective. However, ectopic expression of a transgene under the rat synapsin 1 promoter was also detected in testis from some transgenic mouse lines. Here we investigate which cells within the testis express a transgene consisting of the rat synapsin 1 promoter fused with luciferase. Synapsin 1-luciferase expression vectors were introduced into HeLa cells, into TM3 cells derived from mouse testicular Leydig cells, and into one-cell embryos to make transgenic mice. Indirect immunofluorescence suggests that nontransfected TM3 cells do not express endogenous synapsin 1. TM3 stable transfectants, however, expressed luciferase under the direction of the synapsin 1 promoter, in both promoter orientations. HeLa cells displayed only low levels of activity. Transgenic mice carrying the synapsin 1-luciferase construct displayed high levels of luciferase activity in the brain, spinal cord, and testis. Enriched populations of prepuberal types A and B spermatogonia and adult Leydig cells, pachytene spermatocytes, and round spermatids prepared from transgenic mice all displayed substantial luciferase activity. Thus, the rat synapsin 1 promoter can mediate reporter gene expression in neurons and testicular cell types.

Too many pediatric trampoline injuries.

BACKGROUND: Recent reports note a dramatic increase in the number of pediatric trampoline injuries (PTI) during the past several years. In 1996, the US Consumer Product Safety Commission estimates that 83 000 patients received treatment for trampoline injuries in US hospital emergency departments (EDs), and that approximately 75% of these patients were <15 years of age. We sought to review our experience with PTI since our previous report (Pediatrics 1992;89:849), and to determine if the American Academy of Pediatrics' current (Pediatrics 1981;67:438) safety recommendations are adequate. METHODS: Retrospective medical record review of all PTI patients presenting to the pediatric ED from November 1990 through November 1997. RESULTS: A total of 727 PTI patients were included; medical records were unavailable for 3 patients. The annual number of PTI nearly tripled during the study period, from 51 in 1991 to a peak of 148 in 1996. PTI patients were 53% female, with a median age of 7 years; 37% were <6 years of age. Privately owned trampolines accounted for 99% of PTI. Most injuries (66%) occurred on the trampoline, 28% resulted from falls off, and 4% from imaginative mechanisms. One hundred eleven patients (15%) suffered severe injury (1990 Abbreviated Injury Scale value >/=3), usually of an extremity (89 out of 111). Fractures occurred in 324 patients (45%). Spinal injuries were common (12%), including 7 patients with cervical or thoracic fractures, and 1 with C7 paraplegia. Fractures were more frequently associated with falls off the trampoline, whereas spinal injuries more frequently occurred on the trampoline. Eighty patients (11%) required prehospital medical transport to our ED, 584 (80%) had ED radiographs, and 382 (53%) required pediatric surgical subspecialty involvement. Seventeen percent of PTI patients (125 out of 727) were admitted to the hospital, including 9 to the pediatric intensive care unit; 99 (14%) required one or more operations. Mean hospital stay was 2 days (range, 1-63 days); 24 stays (19%) were for >/=3 days. We estimate that the hospital charges for the acute medical care of PTI study patients at our institution totaled approximately $700 000. CONCLUSIONS: PTI are dramatically increasing in number, and result in considerable childhood morbidity. Most PTI occur on privately owned trampolines. Few, if any, safety recommendations for the trampoline are followed. We support recommendations for a ban on the recreational, school, and competitive pediatric use of trampolines.

Analysis and modulation of DNA repair in aging.

Nearly 40 years ago it was proposed that accumulation of mutations or increased levels of DNA damage might contribute to aging processes. Despite several correlative studies in this area, the answer as to whether genomic integrity contributes to aging has remained illusive. More recently it has been hypothesized that decreased mitochondrial DNA integrity plays a role in aging. To begin to test these hypotheses more directly, we are developing transgenic mouse and cell culture model systems. For example, transgenic mice overexpressing the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) have been made and have a reduced spontaneous frequency of hepatocellular carcinoma. A lifespan study using the MGMT transgenic mice is in progress in an effort to determine whether cancer impacts on the median or maximal lifespan of a species. Second, a quantitative PCR technique is being used to measure mitochondrial DNA damage in mitotic and post-mitotic cells to determine if the level of damage and/or repair is different based on mitotic status. Finally, mice deficient in metallothionein-I and -II are being used in an effort to determine if the subcellular distribution of metals impact on oxidative damage with increased age.

Xrcc-1 expression during male meiosis in the mouse.

XRCC1 is involved in DNA strand-break repair, homologous recombination, and sister chromatid exchange and is expressed as a low-abundance mRNA with elevated expression in testis. The purpose of this study was to determine whether specific spermatogenic cell types have elevated Xrcc-1 expression and whether expression levels change in the testis with increased age. Northern blot analysis of mRNA prepared from testes of 15-, 25-, and 60-day-old mice revealed a single hybridizing band of 2.2 kb. Quantitative RNase protection assays revealed no changes in the level of Xrcc-1 expression in testis relative to DNA content among 6-, 12-, 18-, 24-, or 28-mo-old mice. Finally, reverse transcription coupled polymerase chain reaction amplification results demonstrated that Xrcc-1 expression is most abundant in pachytene spermatocytes and round spermatids with low expression in Sertoli cells, types A and B spermatogonia, preleptotene spermatocytes, and leptotene plus zygotene spermatocytes. The relatively abundant Xrcc-1 expression in pachytene spermatocytes and round spermatids suggests that Xrcc-1 is involved in DNA strand-break repair associated with meiotic recombination in addition to its previously implicated role in strand-break repair associated with base excision repair.