Investigations on vitamin D esters synthesized in rats. Turnover and sites of synthesis

1. The tissue contents of vitamin D alcohol and ester were estimated in rats 5, 10, 24, 48 and 72hr. after peroral administration of [1-(3)H]cholecalciferol. 2. The total vitamin D in liver decreased in an exponential fashion from 19% of the dose at 5hr. to 0.6% at 72hr., but the ester content remained at a relatively constant low value from 5hr., so that by 72hr. it represented 67% of the total vitamin D. Vitamin D ester in kidney increased slowly to 48hr., but by 72hr. it was only 10% of the total vitamin D. 3. The small intestine, unlike liver and kidney, contained a higher content of vitamin D ester 10hr. after administration than at later times, and it is postulated that some vitamin D was esterified during absorption from the alimentary tract. 4. Plasma contained vitamin D ester at all time intervals, and it is suggested that ester found in liver and kidney could have been transported to these sites in the blood. 5. Thoracic-duct lymph was found to transport 43% of a peroral dose of vitamin D in 12hr., of which 1.4% was esterified. The fatty acid components of the lymph vitamin D ester, determined by two-dimensional thinlayer chromatography, were mainly palmitate (31%), stearate (25%), oleate (16%) and linoleate (16%). This pattern was similar to that previously found in liver.     

Transposon mutagenesis of baculoviruses: analysis of TFP3 lepidopteran transposon insertions at the FP locus of nuclear polyhedrosis viruses

We report the complete sequences of two representatives of the TFP3 transposable element family of the lepidopteran, Trichoplusia ni. These elements were isolated as insertions mobilized from the Lepidopteran host genome into two closely related nuclear polyhedrosis viruses (NPV) during infection. Both elements inserted within the 500-bp FP locus of the respective viral genomes (map units 36.0 to 37.0), causing a distinctive plaque morphology phenotype and the loss of a 25-kDa viral-specific protein. Both insertions occurred at the identical TTAA target site in the respective genomes, in the same relative orientation, and are flanked by 15-bp imperfect inverted repeats. The inserted elements interrupt the 25K open reading frame (ORF). One of these FP mutants undergoes spontaneous reversion. Sequence analysis at the excision site of a spontaneous revertant demonstrates that the TFP3 elements are capable of precise excision, restoring the expression of the 25-kDa protein. We also compare the sequences of the 25K genes of the Autographa californica and Galleria mellonella viruses (AcMNPV and GmMNPV, respectively). The 25K gene sequences diverge in five areas, resulting in an additional EcoRV and TaqI site within the GmMNPV 25K gene, and extension of the ORF for an additional 2 amino acids at the C-terminus of the predicted GmMNPV 25 kDa protein. The phenomenon of transposon mutagenesis of Baculovirus genomes provides a unique opportunity for analysis of transposon mobility.