Biomedical subjects

Q J Hu

Publications and source records attributed to Q J Hu.

4 recordsLinked to original sources

PubMed1996

The adjacent pixel nonlinearity: problems and solutions.

The adjacent pixel nonlinearity refers to the dependence of the luminance of a given pixel on the preceding pixel or pixels. We measured this nonlinearity for two CRT displays by measuring the average luminances of a variety of test patterns with different luminance jumps. A two-stage model proposed by Mulligan and Stone was used to fit the data [Mulligan, J.B. & Stone, L. S., (1989). Journal of the Optical Society of America A, 6, 1217-1227 (1989)]. The results show that the model predicts our data well. Based on our measurements and the modeling results, a double-entry look-up table was created to compensate for this nonlinearity. This compensation method works even if the current pixel depends on more than one preceding pixel. Observers commented that at small pixel sizes the compensation results in a sharp, accurate image. Advantages and problems of this compensation will be discussed.

Computer Graphics↗

PubMed1992

The retinoblastoma protein physically associates with the human cdc2 kinase.

The protein product (pRB) of the retinoblastoma susceptibility gene functions as a negative regulator of cell proliferation, and its activity appears to be modulated by phosphorylation. Using a new panel of anti-human pRB monoclonal antibodies, we have investigated the biochemical properties of this protein. These antibodies have allowed us to detect a pRB-associated kinase that has been identified as the cell cycle-regulating kinase p34cdc2 or a closely related enzyme. Since this associated kinase phosphorylates pRB at most of the sites used in vivo, these results suggest that this kinase is one of the major regulators of pRB. The associated kinase activity follows the pattern of phosphorylation seen for pRB in vivo. The associated kinase activity is not seen in the G1 phase but appears in the S phase, and the levels continue to increase throughout the remainder of the cell cycle.

Antibodies, Monoclonal↗

PubMed1991

Antibodies specific for the human retinoblastoma protein identify a family of related polypeptides.

Even though the retinoblastoma gene is one of the best-studied tumor suppressor genes, little is known about its functional role. Like all tumor suppressor gene products, the retinoblastoma protein (pRB) is thought to inhibit some aspect of cell proliferation. It also appears to be a cellular target of several DNA tumor virus-transforming proteins, such as adenovirus E1A, human papillomavirus E7, or simian virus 40 large T antigen. To help in the analysis of pRB, we have prepared a new set of anti-human pRB monoclonal antibodies. In addition to being useful reagents for the study of human pRB, these antibodies display several unexpected properties. They can be used to distinguish different subsets of the pRBs on the basis of their phosphorylation states. Some are able to recognize pRB homologs in other species, including mice, chickens, and members of the genus Xenopus. In addition, some of these antibodies can bind directly to other cellular proteins that, like pRB, were originally identified through their association with adenovirus E1A. These immunologically cross-reactive proteins include the p107 and p300 proteins, and their recognition by antibodies raised against pRB suggests that several members of the E1A-targeted cellular proteins form a structurally and functionally related family.

Adenovirus Early Proteins↗

PubMed1990

The regions of the retinoblastoma protein needed for binding to adenovirus E1A or SV40 large T antigen are common sites for mutations.

The protein product of the retinoblastoma (RB) gene is thought to function in a pathway that restricts cell proliferation. Recently, transforming proteins from three different classes of DNA tumor viruses have been shown to form complexes with the RB protein. Genetic studies suggest that these interactions with the RB protein are important steps in transformation by these viruses. In order to understand better the function of the RB-viral oncoprotein complexes, we have mapped the regions of the RB protein that are necessary for these associations. Two non-contiguous regions of RB were found to be essential for complex formation with adenovirus E1A or SV40 large T antigen. These two regions are found between amino acids 393 and 572 and 646 and 772. Interestingly, these binding sites on RB overlap with the positions of naturally occurring, inactivating mutations of the RB gene. These results strongly suggest that these viral oncoproteins are targeting a protein domain that is an important site in the normal function of the RB protein.

Adenovirus Early Proteins↗