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Biomedical subjects

R Richards

Publications and source records attributed to R Richards.

156 records · Page 9Linked to original sources
PubMedDate not supplied

Regulation of the synthesis and release of decidual prolactin by placental and autocrine/paracrine factors.

Human decidual tissue synthesizes and secretes a protein that is identical to pituitary prolactin in its chemical, biological and immunological properties. Nevertheless, the factors that regulate the synthesis and release of prolactin from the decidual tissues appear to be different to those regulating the synthesis and release of pituitary prolactin. Studies from our laboratory over the past few years indicate that the synthesis and release of decidual prolactin are regulated, at least in part, by factors released by placenta, fetal membranes and decidua. The placenta releases a 23.5 KMr protein [decidual prolactin-releasing factor (PRL-RF)] that stimulates a rapid release of prolactin within the first few minutes of exposure and a sustained, prolonged, increase in the synthesis and release of prolactin beginning 6-8 h after exposure. The acute release of prolactin in response to PRL-RF is inhibited by decidual prolactin release-inhibitory factor (PRL-IF), a 35-45 K Mr protein that is released by the decidua. The secondary increase in the synthesis and release of prolactin in response to PRF-RF is blocked by lipocortin I, which is synthesized by both the placenta and decidua. IGF-I, insulin and relaxin also stimulate the synthesis and release of prolactin. However, the stimulation in response to these factors does not occur until 24-48 h after exposure. The cellular mechanisms involved in the release of decidual prolactin are as yet unknown. However, recent studies implicate activation of adenylate cyclase, phospholipase C-mediated phosphoinositide hydrolysis and phospholipase A2-mediated arachidonic acid release in the regulation of prolactin release. The finding that the synthesis and release of decidual prolactin are regulated, at least in part, by PRL-RF, IGF-I, insulin, relaxin and lipocortin I strongly suggests that there is novel feedback regulation between the placenta, fetal membranes, and decidua in the regulation of the synthesis and release of decidual prolactin.

Annexins↗
PubMedDate not supplied

Characterization of a lung epithelial cell strain with potential applications in toxicological studies.

An epithelial cell strain (LEC, lung epithelial cells) was established from the lungs of an adult Fischer-344 rat. The cells had properties of normal, untransformed cells in culture which include contact inhibition of growth, inability to grow in soft agar, and inability to form tumors when injected subcutaneously into syngeneic hosts. Low passage LEC were diploid, while high passage cells were aneuploid with an extra chromosome. LEC resembled type II alveolar cell in vivo in that they had lamellar inclusions in their cytoplasm, microvilli on cell surface, and that they could incorporate [14C] choline into disaturated phosphatidyl choline, a surfactant lipid. The ability of LEC to activate procarcinogens was demonstrated by co-cultivation of LEC with Chinese hamster ovary (CHO) cells in the presence of procarcinogens benzo[a]pyrene and 3-methyl cholanthrene. While these procarcinogens were non-mutagenic to CHO cells which lacked the metabolic activation capacity, they were mutagenic when LEC were co-cultured with the CHO cells. By maintaining LEC cells on collagen gel without overlying medium, the cells could be directly exposed to noxious airborne agents. Using this technique, the cytotoxicity of NO2 was detected. Because of the lung epithelial origin, the ability to metabolize xenobiotics, and the exposure system to airborne agents, the LEC strain can be a useful and relevant in vitro system for the toxicological studies of inhalable materials.

Animals↗
PubMedDate not supplied

The M1 subunit of rat liver ribonucleotide reductase appears to be modified by ubiquitination.

Using a combination of immunoblotting, double immunoprecipitation, immunoglobulin-affinity chromatography, and isoelectrofocusing, we have been able to identify a group of proteins that display CDP-reductase activity and contain antigenic epitopes recognized by anti-ribonucleotide reductase M1 subunit and anti-ubiquitin antibodies. In the cytoplasm of rat liver cells, we could detect a total of five proteins with molecular masses of 92, 89, 56, 45, and 37 kilodaltons which reacted with the anti-M1 subunit serum. All of them, except the 89-kilodalton protein (the nascent unmodified M1), were also recognized by the anti-ubiquitin antibody. In normal liver cells, all of the apparently ubiquitinated species of the M1 protein were found in the cytoplasm, but not in the nuclear envelope associated pool of the enzyme. However, we did not detect ubiquitinated M1 protein fragments in the cytoplasm of Morris hepatoma 5123tc. The level of the apparently ubiquitinated fragments of the M1 subunit increased in parallel to the DNA-synthetic activity of normal liver cells, suggesting that ubiquitination plays a key role in the regulation of the activity of the enzyme during the cell cycle.

Amino Acid Sequence↗
PubMedDate not supplied

Pseudo-shading technique in the two-dimensional domain: a post-processing algorithm for enhancing the Z-buffer of a three-dimensional binary image.

Three-dimensional (3D) medical graphics is becoming popular in clinical use on tomographic scanners. Research work in 3D reconstructive display of computerized tomography (CT) and magnetic resonance imaging (MRI) scans on conventional computers has produced many so-called pseudo-3D images. The quality of these images depends on the rendering algorithm, the coarseness of the digitized object, the number of grey levels and the image screen resolution. CT and MRI data are fundamentally voxel based and they produce images that are coarse because of the resolution of the data acquisition system. 3D images produced by the Z-buffer depth shading technique suffer loss of detail when complex objects with fine textural detail need to be displayed. Attempts have been made to improve the display of voxel objects, and existing techniques have shown the improvement possible using these post-processing algorithms. The improved rendering technique works on the Z-buffer image to generate a shaded image using a single light source in any direction. The effectiveness of the technique in generating a shaded image has been shown to be a useful means of presenting 3D information for clinical use.

Algorithms↗
PubMedDate not supplied

Exertion-induced heat exhaustion and other medical aspects of the City-to-Surf fun runs, 1978-1984.

During the years 1978 to 1984, only 197 (0.14%) of 144 950 starters in a 14-km road race had suffered from heat exhaustion; of these, only three (1.5%) required admission to hospital. The effectiveness of treatment in medical centres was indicated by the fact that the mean time taken for the body temperature to fall to 38 degrees C was 31 +/- 12 minutes in all heat-exhaustion casualties, and 49 +/- 14 minutes in 41 subjects who had rectal temperatures of 42 degrees C and higher. When disaster teams from metropolitan hospitals were introduced in 1983, it became apparent that skilled staff members, despite their lack of experience in the resuscitation of combative heat casualties, could carry out the established procedures and protocols effectively and efficiently.

Adult↗
PubMedDate not supplied

Method of predicting the number of casualties in the Sydney City-to-Surf fun runs.

A simple and effective method of predicting the number of casualties who may require urgent medical attention, which is based on previous experience in the City-to-Surf fun runs, including weather forecasts and number of entries, is described. In 1983 and 1984, the method was used to predict a number of casualties which was found to be consistent with the actual number. As a result of these predictions, the human and material resources were deployed effectively and all casualties were treated efficiently.

Australia↗