Absolute Calibration of a Large-diameter Light Source

A method of absolute calibration for large aperture optical systems is presented, using the example of the Pierre Auger Observatory fluorescence detectors. A 2.5 m diameter light source illuminated by an ultra--violet light emitting diode is calibrated with an overall uncertainty of 2.1 % at a wavelength of 365 nm.Comment: 15 pages, 8 figures. Submitted to JINS

Absolute Calibration of the Auger Fluorescence Detectors

Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the ombined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.Comment: 4 pages, 3 figure. Submitted to the 29th ICRC, Pune, Indi

Ekspresi Gen Aromatase pada Pengarahan Diferensiasi Kelamin Ikan Nila (Oreochromis Niloticus Linnaeus 1758) Menggunakan Madu [Aromatase Gene Expression Of Sex Reversal Nile Tilapia (Oreochromis Niloticus Linnaeus 1758) Using Honey]

Budi daya ikan nila dengan populasi jantan semua (monoseks) lebih memberikan keuntungan karena laju pertumbuhan-nya lebih cepat dan dapat mencegah pemijahan liar.Teknik pengarahan diferensiasi kelamin(sex reversal) digunakan untuk mengarahkan pembentukan jenis kelamin pada budi daya ikan.Penelitian ini dilakukan untuk mengevaluasi pe-ngaruh perendaman larva ikan nila menggunakan tiga sumber madu berbeda terhadap persentase ikan jantan dan ekspresi gen aromatase. Pada percobaan satu, 30 larva ikan nila berumur 12 hari setelah menetas direndam menggunakan madu hutan, madu ternak dan madu bakau, dengan dosis 10 ml L-1 air selama 10 jam. Ikan dipelihara dalam kondisi yang sama selama dua bulan. Hasil penelitian menunjukkan bahwa persentase ikan jantan tidak berbeda nyata antar perlakuan madu (p>0,05), tetapi semuanya berbeda nyata dengan kontrol (p<0,05). Pada percobaan kedua, larva ikan nila direndam dalam air mengandung dua bahan bioaktif madu, yakni chrysin dan kalium dengan dosis masing-masing 20 mg L-1 dan 0,026 g L-1. Ekspresi gen aromatase tipe gonad (aroma-g) dan tipe otak (aroma-o) dianalisis menggunakan metode RT-PCR. Sampel jaringan diambil pada waktu 1, 6, 12, 24, dan 48 jam pascaperlakuan madu, chrysin, dan kalium, serta setelah ikan berumur dua bulan.Ukuran fragmen DNA aromatase pada gonad betina sekitar 200 bp. Perendaman chrysin dan kalium meningkatkan persentase ikan jantan (p<0,1). Analisis RT-PCR menunjukkan bahwa madu, chrysin, dan kalium dapat menekan ekspresi gen aroma-g pada jam ke-12 pascaperendaman. Dengan demikian dapat disimpulkan bahwa madu, chrysin dan kalium dapat digunakan untuk pengarahan diferensiasi ikan nila, dan mekanis-menya seperti penghambat aromatase

Multi-wavelength Calibration Procedure for the Pierre Auger Observatory Fluorescence Detectors

We present a method to measure the relative spectral response of the Pierre Auger Observatory Fluorescence Detector. The calibration was done at wavelengths of 320, 337, 355, 380 and 405 nm using an end-to-end technique in which the response of all detector components are combined in a single measurement. A xenon flasher and notch-filters were used as the light source for the calibration device. The overall uncertainty is 5%.Comment: Submitted to Astroparticle Physics. V2: section 5.2 extended; author list change

Class II Transactivator: Mastering the Art of Major Histocompatibility Complex Expression

Great progress in understanding the relative importance of various portions of CIITA for transcriptional activation of class II MHC genes has been made since CIITA's discovery in 1993. Emerging from these studies is a fairly consistent picture where CIITA is expressed, binds GTP, translocates to the nucleus, and interacts with specific DNA-binding transcription factors and basal transcription components, thus opening and activating class II MHC and related promoters. Despite these strides, this model is essentially unchanged from that initially espoused. The observation that class II MHC promoters in some B cells are bound to X and Y box binding proteins and thus open even in the absence of CIITA, whereas these same promoters in non-B cells are closed until CIITA is present, is provocative. One potential explanation is that CIITA possesses two distinct functions, the ability to direct the opening of responsive promoters (presumably through some form of remodeling) and the ability to activate transcription through its activation domain and protein-protein interactions (132, 141). The presence of a locus control region responsive to a B-cell-specific factor is another possibility, yet CIITA must, in some fashion, be directing chromatin remodeling in cells which can be induced to express CIITA. While CBP is an obvious candidate for mediating remodeling, no conclusive experiments have shown that CBP is required for the remodeling of class II MHC promoters. The studies above support interactions between CIITA and transcription factors, but does CIITA merely bind these factors to place the activation domain appropriately? Why has it been difficult to demonstrate a role for CIITA in a transcription complex? Is GTP binding only essential for nuclear import? Is nuclear export of CIITA occurring and is it relevant? What aspect of class II MHC transcription requires that retinoblastoma protein Rb be present? Is CIITA a prototype for a family of transcriptional coactivators? Why is limited class II expression observed in the absence of CIITA? The evolutionary conservation of W-, X-, and Y-containing promoters in mammals, birds (104), amphibians (51), and fish (121) suggests that CIITA may be extremely old; what are its origins? All remaining questions aside, CIITA is truly a remarkable protein. Controlled by up to four separate promoters, CIITA has been imparted a complex pattern of inducible and constitutive expression that can be regulated in developmental pathways. Through exercising specific control over the transcription of every major component of class II MHC antigen presentation pathway, CIITA gains the title of a master regulator. As CIITA appears to be class II MHC specific, it can be thought of as the core transcription factor of which all the remaining components are but cofactors. This is central to the concept of CIITA as a scaffolding protein or integrator and perhaps alters our view of transcriptional control away from promoters and individual factors towards a more unified enhanceosome perspective. The view of CIITA as a master regulator has implications for practical applications that are staggering. Successful engineering of dominant-negative CIITAs may lead to the production of transplant tissues unable to express class II MHC and the associated self peptides which contribute so significantly to graft rejection. A thorough understanding of CIITA's molecular mechanisms may lead to therapeutics which allow temporary enhancement or suppression of class II MHC, thus favorably altering the immune response during critical events in pathogenesis, autoimmune disease, tumorigenesis, and neuroinflammation

The Histone Acetyltransferase Domains of CREB-binding Protein (CBP) and p300/CBP-associated Factor Are Not Necessary for Cooperativity with the Class II Transactivator

The class II transactivator (CIITA) is a transcriptional co-activator regulating the constitutive and interferon-gamma-inducible expression of class II major histocompatibility complex (MHC) and related genes. Promoter remodeling occurs following CIITA induction, suggesting the involvement of chromatin remodeling factors. Transcription of numerous genes requires the histone acetyltransferase (HAT) activities of CREB-binding protein (CBP), p300, and/or p300/CBP-associated factor (pCAF). These co-activators cooperate with CIITA and are hypothesized to promote class II major histocompatibility complex transcription through their HAT activity. To directly test this, we used HAT-defective CBP and pCAF. We demonstrate that cooperation between CIITA and CBP is independent of CBP HAT activity. Further, although pCAF enhances CIITA-mediated transcription, pCAF HAT domain dependence appears contingent upon the concentration of available CIITA. When HAT-defective CBP and pCAF are both present, cooperativity with CIITA is maintained. Consistent with a recent report, we show that nuclear localization of CIITA is enhanced by lysine 144, an in vitro target of pCAF-mediated HAT. Yet we find that neither mutation of lysine 144 nor deletion of residues 132-209 affects transcriptional cooperation with CBP or pCAF. Thus, acetylation of this residue may not be the primary mechanism for pCAF/CBP cooperation with CIITA. In conclusion, the HAT activities of the co-activators are not necessary for cooperation with CIITA