Correlation of spinal epidural fat volume with body mass index: a longitudinal study.

PURPOSE: Spinal epidural lipomatosis is abnormal accumulation of normal fat in the epidural space with weight loss suggested as first-line therapy in select symptomatic patients. However, moderate to large longitudinal studies establishing concordant changes between body mass index and epidural fat are lacking. The purpose of this study was to longitudinally assess this relationship. METHODS: We performed an ancillary study of the Habitual Diet and Avocado Trial. Baseline and six-month abdominal MRIs were analyzed for 98 overweight or obese but otherwise healthy subjects. Dorsal epidural fat volumes in the lumbar spine were measured and correlated with changes in body mass index, changes in visceral fat volume, and demographic information. RESULTS: There was a linear relationship between body mass index changes and epidural fat volume changes with a one-point change in body mass index corresponding to a 45 mm3 change in dorsal epidural fat volume (p < 0.001, 95% CI 31.87 to 76.77) as well as between visceral fat volume changes and epidural fat volume changes (regression coefficient 0.51, p < 0.001, 95% CI 0.22 to 0.47). Age was inversely related with subjects older than 45.7 years tending to lose epidural fat (regression coefficient -0.22, p = 0.025, 95% CI -10.43 to -0.72). CONCLUSION: Changes in spinal dorsal epidural fat volume parallel changes in body mass index and visceral fat, supporting weight loss as initial treatment for uncomplicated obesity-associated spinal epidural lipomatosis.

Resident-attending discrepancy rates for two consecutive versus nonconsecutive weeks of overnight shifts.

PURPOSE: Recent Accreditation Council for Graduate Medical Education policy changes no longer limit the number of consecutive night shifts allowed for trainees. Few studies have examined radiology resident overnight performance over time. This study aimed to compare significant resident-attending discrepancy rates for residents working 2 nonconsecutive versus consecutive weeks of overnight shifts. The authors hypothesized significantly increased week-two discrepancies in the consecutive group. METHODS: For 2020, a retrospective analysis of significant overnight resident-attending discrepancy rates over a 24-week period using database searches was performed for residents self-selecting 2 nonconsecutive versus consecutive weeks. The nonconsecutive group typically had a 7-day mix of days off and day shifts between their night shift weeks. Paired and unpaired t tests were performed with p < 0.05 considered significant. RESULTS: For the 24 sets of 2 weeks covered by two residents at a time, eight were nonconsecutive and 16 were consecutive. The nonconsecutive group had 75.0% R4 coverage compared to 37.5% for the consecutive group. There were no significant study volume differences between the groups. A total of 27,906 studies (35.3% cross-sectional [CT and MR], 54.9% radiograph plus fluoroscopy, 9.8% US) were performed with 223 discrepancies (0.80%). Overall discrepancies for the nonconsecutive versus consecutive groups were 39/4505 (0.87%) versus 59/9462 (0.62%; p = 0.32) for week one and 46/4732 (1.0%) versus 79/9207 (0.86%; p = 0.60) for week two with no significant differences between the groups by modality. CONCLUSION: Residents self-selecting 2 consecutive weeks of overnight shifts do not have increased resident-attending discrepancy rates compared to 2 nonconsecutive weeks.

Agrobacterium-mediated transformation of maize (Zea mays) with Cre-lox site specific recombination cassettes in BIBAC vectors.

The Cre/loxP site-specific recombination system has been applied in various plant species including maize (Zea mays) for marker gene removal, gene targeting, and functional genomics. A BIBAC vector system was adapted for maize transformation with a large fragment of genetic material including a herbicide resistance marker gene, a 30 kb yeast genomic fragment as a marker for fluorescence in situ hybridization (FISH), and a 35S-lox-cre recombination cassette. Seventy-five transgenic lines were generated from Agrobacterium-mediated transformation of a maize Hi II line with multiple B chromosomes. Eighty-four inserts have been localized among all 10 A chromosome pairs by FISH using the yeast DNA probe together with a karyotyping cocktail. No inserts were found on the B chromosomes; thus a bias against the B chromosomes by the Agrobacterium-mediated transformation was revealed. The expression of a cre gene was confirmed in 68 of the 75 transgenic lines by a reporter construct for cre/lox mediated recombination. The placement of the cre/lox site-specific recombination system in many locations in the maize genome will be valuable materials for gene targeting and chromosome engineering.

A test for ectopic exchange catalyzed by Cre recombinase in maize.

A maize line expressing Cre recombinase as well as the recipient line without the transgene were assayed for evidence of ectopic recombination within the maize genome. Such a test is valuable for understanding the action of Cre as well as for its use to recombine two target lox sites present in the chromosomes. Pollen examination and seed set tests of material expressing Cre provided no evidence of ectopic recombination, which would be manifested in the production of translocations or inversions and result in pollen abortion and reduced seed set. Root-tip chromosome karyotype analysis was also performed on material with and without Cre expression. Chromosomal aberrations in Cre+ material were not observed above the background level.