984 resultados para fourth instar
Resumo:
Chromosome-specific gene regulation is known thus far only as a mechanism to equalize the transcriptional activity of the single male X chromosome with that of the two female X chromosomes. In Drosophila melanogaster, a complex including the five Male-Specific Lethal (MSL) proteins, “paints” the male X chromosome, mediating its hypertranscription. Here, with the molecular cloning of Painting of fourth (Pof), we describe a previously uncharacterized gene encoding a chromosome-specific protein in Drosophila. Unlike the MSL proteins, POF paints an autosome, the fourth chromosome of Drosophila melanogaster. Chromosome translocation analysis shows that the binding depends on an initiation site in the proximal region of chromosome 4 and spreads in cis to involve the entire chromosome. The spreading depends on sequences or structures specific to chromosome 4 and cannot extend to parts of other chromosomes translocated to the fourth. Spreading can also occur in trans to a paired homologue that lacks the initiation region. In the related species Drosophila busckii, POF paints the entire X chromosome exclusively in males, suggesting relationships between the fourth chromosome and the X and between POF complexes and dosage-compensation complexes.
Resumo:
Bombesin is a tetradecapeptide originally isolated from frog skin and demonstrated to have a wide range of actions in mammals. Based on structural homology and similar biological activities, gastrin-releasing peptide (GRP) has been considered the mammalian equivalent of bombesin. We previously reported that frogs have both GRP and bombesin, which therefore are distinct peptides. We now report the cloning of a bombesin receptor subtype (BB4) that has higher affinity for bombesin than GRP. PCR was used to amplify cDNAs related to the known bombesin receptors from frog brain. Sequence analysis of the amplified cDNAs revealed 3 classes of receptor subtypes. Based on amino acid homology, two classes were clearly the amphibian homologs of the GRP and neuromedin B receptors. The third class was unusual and a full-length clone was isolated from a Bombina orientalis brain cDNA library. Expression of the receptor in Xenopus oocytes demonstrated that the receptor responded to picomolar concentrations of [Phe13]-bombesin, the form of bombesin most prevalent in frog brain. The relative rank potency of bombesin-like peptides for this receptor was [Phe13]bombesin > [Leu13]bombesin > GRP > neuromedin B. In contrast, the rank potency for the GRP receptor is GRP > [Leu13]bombesin > [Phe13]bombesin > neuromedin B. Transient expression in CHOP cells gave a Ki for [Phe13]bombesin of 0.2 nM versus a Ki of 2.1 nM for GRP. Distribution analysis showed that this receptor was expressed only in brain, consistent with the distribution of [Phe13]-bombesin. Thus, based on distribution and affinity, this bombesin receptor is the receptor for [Phe13]bombesin. Phylogenetic analysis suggests that this receptor separated prior to separation of the GRP and neuromedin B receptors; thus, BB4 receptors and their cognate ligands may also exist in mammals.
Resumo:
Recently the Supreme Court has placed new limits on both the substance of the Fourth Amendment and the exclusionary that serves as the principal remedy for Fourth Amendment violations. In this Article we briefly summarize these limitations and then argue that the curtailment of the exclusionary rule has the potential to ameliorate substantive Fourth Amendment doctrine. The limited reach of the modern exclusionary rule provides the Court with license to develop an expansive new substantive framework free of the specter of a correspondingly expansive remedial framework. One point on which nearly all jurists and commentators agree is that current Fourth Amendment doctrine is a mess. We argue that the Court’s exclusionary rule cases, while frustrating and ill-conceived if viewed in isolation, provide the Court with an opportunity to revisit problematic Fourth Amendment doctrine that was born under a very different remedial regime. Such an approach would allow the Court to adhere to its current view of the exclusionary rule as a remedy of last resort while creating a Fourth Amendment with teeth. The goal is a Fourth Amendment right that is more substantial and clearly defined, but a remedy that remains limited to egregious violations of clear substantive rules. The time is now to lift the Fourth Amendment fog.
Resumo:
Floor plan of renovations for the third and fourth floors of Hollis Hall, as drawn by William Rotch Ware in 1874. Includes dimensions for Pi Eta Society rooms, student chambers, hallways, and coal furnaces.
Resumo:
Floor plan of renovations for the third and fourth floors of Stoughton Hall, as drawn by William Rotch Ware in 1874. Includes dimensions for student chambers, H.P. Club Rooms, hallways, and coal furnaces.
Resumo:
cura et sumptibus Matth. Seutteri.