Biomedical subjects

L B Bender

Publications and source records attributed to L B Bender.

5 recordsLinked to original sources

PubMed1995

Silkworm TFIIIA requires additional class III factors for commitment to transcription complex assembly on a 5S RNA gene.

We find striking similarities in promoter structure and requirements for template commitment on 5S RNA and tRNA genes from silkworms. The promoters are nearly the same size (approximately 160 bp) and include flanking as well as internal sequences. To analyze the factor requirements for 5S RNA transcription complex assembly in a completely homologous system, we have isolated a silkworm fraction that is highly enriched for the 5S RNA-specific transcription factor, TFIIIA. Using this fraction, together with the other silkworm fractions, TFIIIB, TFIIIC, TFIIID and RNA polymerase III, we demonstrate that the requirements for 5S RNA transcription complex assembly are very similar to those previously established for a tRNA(C)(Ala) gene. Specifically, no individual factor fraction is sufficient for commitment of silkworm 5S RNA genes to transcription complex assembly. Rather, combinations of at least three factor fractions are required. Our observation that more than one subset of factors is competent for commitment suggests that silkworm 5S RNA genes further resemble tRNA(C)(Ala) genes in their ability to use multiple pathways for transcription complex formation.

Animals↗

PubMed1993

Complex function and expression of Delta during Drosophila oogenesis.

Delta (Dl) encodes a cell surface protein that mediates cell-cell interactions central to the specification of a variety of cell fates during embryonic and postembryonic development of Drosophila melanogaster. We find that the Delta protein is expressed intermittently in follicle cells and in germ-line cells during stages 1-10 of oogenesis. Furthermore, Delta expression during oogenesis can be correlated with a number of morphogenetic defects associated with sterility observed in Dl mutant females, including failure of stalk formation within the germarium and subsequent fusion of egg chambers, necrosis in germ-line cells, and multiphasic embryonic arrest of fertilized eggs. We have also identified a Dl mutation that leads to context-dependent defects in Dl function during oogenesis. Direct comparison of Delta protein expression with that of the Notch protein in the ovary reveals substantial, but incomplete, coincidence of expression patterns in space and time. We discuss possible roles for the Delta protein in cell-cell interactions required for cell fate specification processes during oogenesis in light of available developmental and histochemical data.

Alleles↗

PubMed1991

Isolation and characterization of the prune locus of Drosophila melanogaster.

The complementary lethal interaction between the prune (pn) and Killer of prune loci of Drosophila melanogaster is an unusual and highly specific phenomenon. A lesion in pn results in a brownish-purple color of the compound eyes, while the conditional dominant Killer of prune mutation exhibits no phenotype by itself. However, a hemizygous or homozygous pn mutant carrying a copy of the Killer of prune gene dies during the late second to third instar stage of larval development. As a step toward understanding the molecular nature of this lethality and the role of pn in pigment biosynthesis, we have cloned the pn locus by using a transposon tag in the P element-induced allele, pn38. In addition, seven independent revertant lines were generated by the remobilization of transposons in pn38. The pn gene is located in a region that is transcriptionally active, and the isolated cDNAs that correspond to this area fall into three transcription units: I, II and III. Southern analysis shows that the restriction fragment length polymorphisms in five pn alleles are localized within a 1.2-kilobase genomic fragment, of which only transcription unit II is a part. The cDNA of this unit recognizes 1.65- and 1.8-kilobase messages in wild-type Drosophila adult head and body tissues that are absent or extremely reduced in pn mutants. Taken together, the results suggest that transcription unit II defines a part of the pn locus and its cDNA encodes a putative structural gene of pn.

Animals↗

PubMed1991

Fused rhabdomeres (fur) in Drosophila: an eye mutation that alters rhabdomere morphology and retinal function.

In the Drosophila compound eye, the photoreceptor cells are organized in highly precise units, the ommatidia. In each photoreceptor cell, the primary photopigment, opsin, is contained in the rhabdomere, an ordered array of densely packed microvilli. A genetic and phenotypic analysis of a new X-linked. P element-induced mutation, fur, (fused rhabdomeres) is presented. Light and electron microscope studies show that mutations at the fur locus result in the fusion of the adjacent rhabdomeres in the developing eye and the fusion takes place during the pupal stage of eye development. Electrophysiological experiments indicate that the fur mutant photoreceptors have reduced sensitivity to light and lack a PDA (prolonged depolarizing afterpotential), a response characteristic of normal photoreceptor cells. Recombination and deficiency mapping localize fur to the proximal region of the X chromosome. Reversion analysis indicates the fur mutant is the result of a P element insertion. These studies suggest that the fur locus encodes a gene that has specific roles in rhabdomere morphogenesis and retinal function.

Animals↗

PubMed1989

Financial analysis of an inner-city helicopter service: charges versus collections.

Trauma centers are now being perceived as financial burdens because of recent changes in trauma reimbursement for the Medicare Prospective Payment System population and the perception that collection rates are lower among trauma patients. We examined the demographic and clinical factors associated with the collection experience in a series of 114 trauma patients transferred by helicopter from the accident site to an inner-city trauma center. Factors affecting payment at 30, 60, 90, and 180 days included patient age, insurance class, and discharge status. While not as high as the collection rate for the facility as a whole, we found an average 71.2% collection rate for trauma patients at 180 days. As long as trauma reimbursement continues to be cost based for nonMedicare patients, collection rates remain an important consideration in determining the financial viability of trauma centers.

Accounting↗