RESUMO
Diploid germline cells must undergo two consecutive meiotic divisions before differentiating as haploid sex cells. During meiosis I, homologs pair and remain conjoined until segregation at anaphase. Drosophila melanogaster spermatocytes are unique in that the canonical events of meiosis I including synaptonemal complex formation, double-strand DNA breaks, and chiasmata are absent. Sex chromosomes pair at intergenic spacer sequences within the ribosomal DNA (rDNA). Autosomes pair at numerous euchromatic homologies, but not at heterochromatin, suggesting that pairing may be limited to specific sequences. However, previous work generated from genetic segregation assays or observations of late prophase I/prometaphase I chromosome associations fail to differentiate pairing from maintenance of pairing (conjunction). Here, we separately examined the capability of X euchromatin to pair and conjoin using an rDNA-deficient X and a series of Dp(1;Y) chromosomes. Genetic assays showed that duplicated X euchromatin can substitute for endogenous rDNA pairing sites. Segregation was not proportional to homology length, and pairing could be mapped to nonoverlapping sequences within a single Dp(1;Y) Using fluorescence in situ hybridization to early prophase I spermatocytes, we showed that pairing occurred with high fidelity at all homologies tested. Pairing was unaffected by the presence of X rDNA, nor could it be explained by rDNA magnification. By comparing genetic and cytological data, we determined that centromere proximal pairings were best at segregation. Segregation was dependent on the conjunction protein Stromalin in Meiosis, while the autosomal-specific Teflon was dispensable. Overall, our results suggest that pairing may occur at all homologies, but there may be sequence or positional requirements for conjunction.
Assuntos
Pareamento Cromossômico/genética , Eucromatina/genética , Meiose/genética , Cromossomos Sexuais/genética , Animais , Centrômero/genética , Segregação de Cromossomos/genética , DNA Ribossômico/genética , Drosophila melanogaster/genética , Heterocromatina/genética , Hibridização in Situ Fluorescente , Masculino , Espermatócitos/crescimento & desenvolvimento , Cromossomo X/genética , Cromossomo Y/genéticaRESUMO
The facsia iliaca block (FIB) is a relatively new regional technique where local anesthetic is delivered within the fascia iliaca region. Indications for a FIB include surgical anesthesia to the lower extremity after knee, femoral shaft, hip surgery, management of cancer pain or pain secondary to inflammatory conditions of the lumbar plexus, as well as treatment of acute pain in the setting of trauma, fracture, or burns. The FIB may be performed using either a loss of resistance technique or an ultrasound (US)-guided technique; however, the use of US has become commonplace and resulted in improved femoral nerve and obturator nerve motor blocks. The main targets of the FIB are the predominant nerves contained in the fascia iliaca compartment (FIC), namely the femoral nerve and the lateral femoral cutaneous nerve. The FIB US guided technique is beneficial to patients and the possibility to perform FIB should be discussed and coordinated with surgical staff appropriately, considering its superiority to general or epidural anesthesia.
Assuntos
Anestésicos Locais/administração & dosagem , Fáscia/efeitos dos fármacos , Nervo Femoral/efeitos dos fármacos , Bloqueio Nervoso/métodos , Dor Pós-Operatória/prevenção & controle , Fáscia/diagnóstico por imagem , Nervo Femoral/diagnóstico por imagem , Humanos , Dor Pós-Operatória/diagnóstico por imagem , Resultado do TratamentoRESUMO
Sterol regulatory element-binding proteins (SREBPs) activate promoters for key genes of metabolism to keep pace with the cellular demand for lipids. In each SREBP-regulated promoter, at least one ubiquitous co-regulatory factor that binds to a neighboring recognition site is also required for efficient gene induction. Some of these putative co-regulatory proteins are members of transcription factor families that all bind to the same DNA sequence elements in vitro and are often expressed in the same cells. These two observations have made it difficult to assign specific and redundant functions to the unique members of a specific gene family. We have used the chromatin immunoprecipitation (ChIP) technique coupled with a transient complementation assay in Drosophila SL2 cells to directly compare the ability of two members of the CREB/ATF family to function as co-regulatory proteins for SREBP-dependent activation of the HMG-CoA reductase promoter. Results from both of these experimental systems demonstrate that CREB is an efficient SREBP co-regulator but ATF-2 is not.
