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Biomedical subjects

C Chu

Publications and source records attributed to C Chu.

100 records · Page 6Linked to original sources
PubMed1977

Effects of nine N-nitroso compounds on the specific radioactivity of liver proteins after injection of [14C]leucine into rats.

We compared the effect of nine N-nitroso compounds, given by gavage to adult rats, on specific radioactivity of the trichloroacetic acid-precipitable liver proteins, 1 hr after the injection of [14C]leucine. The specific radioactivity was decreased by dimethylnitrosamine, diethylnitrosamine, methyl-n-butylnitrosamine, and nitrosomorpholine 5 to 10 hr after their administration; was increased by nitrosopiperidine, dinitrosopiperazine, and methylnitrosourea 5 to 24 hr after gavage; and was unaffected by nitrososarcosine and nitrosodihydrouracil. With dimethylnitrosamine, specific radioactivity was decreased by 10 but not 5 mg/kg. In control rats and rats given injections of either of two nitrosamines, protein specific radioactivity at 60 min after the [14C]leucine injection was 76 to 87% of that at 30 min, indicating some degradation of the proteins at 60 min. The liver:blood ratio of [14C]cycloleucine concentration was unaffected by four nitrosamines, indicating no effect on leucine transport. The effect of the nine compounds was examined on total pool size of free leucine in the liver, at times close to those for the maximum specific radioactivity effect. For these data, we calculated "corrected specific radioactivity," adjusted for changes in pool size. This adjustment is only a first approximation since, for example, the free leucine pool is not uniform with respect to protein synthesis. The four N-nitroso compounds that decreased specific radioactivity also decreased corrected specific radioactivity, even though they enlarged the leucine pool. Of the remaining compounds, two enlarged the leucine pool and three increased corrected specific radioactivity. For all nine compounds, the decrease in specific and correlated with the ability to cause acute liver necrosis. When nitrosodihydrouracil was excluded, the decrease in specific and corrected specific radioactivity was significantly correlated with the reported liver carcinogenicity.

Animals↗
PubMedDate not supplied

Cross-cultural health issues in contemporary Australia.

In recent decades, Australia has rapidly become one of the more ethnically diverse societies with over 120 different languages groups and 41.9% of the population having at least one parent born overseas. This presents a great challenge for decision-makers and service providers to plan and provide effective and responsive health services for communities with such diverse languages, cultural backgrounds, migration circumstances and socioeconomic status. In order to offer equitable, culturally sensitive and appropriate health services, there is a pressing need to identify and manage cross-cultural health issues. This paper will first clarify concepts fundamental to the understanding of cross-cultural phenomena. It will then discuss several priority migrant health issues including communication breakdown, reproductive health, mental health, workplace health and safety, and doubly disadvantaged groups. Finally it will recommend measures to address the above issues and to promote equity, access and quality in health care for migrants.

Australia↗
PubMedDate not supplied

O-specific side-chain toxin-protein conjugates as parenteral vaccines for the prevention of shigellosis and related diseases.

Only indirect evidence has been cited to document that lipopolysaccharide-mediated virulence at the bacterial level and serum antibodies to the O-specific side chain of the lipopolysaccharide molecule may prevent shigellosis. Our proposed use of the B subunit of Shiga toxin as a carrier protein is based upon evidence (even more indirect) that serum antitoxin may reduce the severity of dysentery and diarrhea. Because animal models of disease may provide information inapplicable to the prediction of vaccine-induced protective immunity, we suggest that clinical trials in the population at risk should be started after successful completion of the safety and immunogenicity phases of vaccine development in laboratory animals and in the target population. Clinical studies of shigella vaccines are difficult because of the many causes of dysentery in a population with a high rate of intestinal disease.

Animals↗
PubMedDate not supplied

A comparison of high-energy accelerator depth dose data.

Accurate depth dose information is necessary for the use of high-energy radiotherapy photon beam units. It would be useful, therefore, to have one set of published data available for each different type unit manufactured to which physicists can compare their measured data. Pertinent questions are raised regarding the similarity between accelerators and their central axis depth dose characteristics, the availability of adequate published central axis depth dose data, and the minimum amount of data needed to determine the applicability of published data to a particular machine. Data taken by the Radiological Physics Center (RPC) for 4-10 MV units are analyzed and compared with published data in an attempt to answer these questions.

Particle Accelerators↗
PubMedDate not supplied

Inflammatory intermediates produced by tissues encasing silicone breast prostheses.

Silicone prostheses, when implanted within the soft tissues of the breast, evoke an inflammatory reaction. In response to silicone exposure, inflammatory mediator production by individual cells has been observed in various experimental studies. In this study, inflammatory mediator production by periprosthetic tissues (whole organ) was measured. The mediator levels were correlated with both the tissue histopathology of the periprosthetic capsules and the clinical symptoms noted by each patient. Tissue surrounding breast implants removed at surgery from ten women (average age and implant duration 40 and 7 years respectively) was cultured in vitro for 24 hours. Control tissues consisting of (a) augmentation mammaplasty skin scars from eight additional patients and (b) knee synovium from seven orthopedic surgery patients with arthritis undergoing primary joint arthroplasty were similarly cultured. The mediators [interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and prostaglandin E2 (PGE2)] liberated into the culture media were measured by an enzyme linked immunosorbent assay. When compared to controls, the mediator levels of IL-6 and TNF-alpha were substantially greater, although IL-2 and PGE2 were lower. Levels varied greatly from patient to patient: in pg/ml per 10 g tissue, IL-2 ranged from 10 to over 1,000; TNF-alpha from 100 to 1,000; IL-6 from 100 to 1,000,000; and PGE2 from 100 to 10,000. The correlation between TNF-alpha and PGE2 levels was .5 between IL-6 and PGE2 was .6, and between IL-6 and TNF-alpha was .77. The correlation between TNF-alpha and IL-6 was statistically significant at a p-value less than .01. Elevated levels of TNF-alpha production were associated with an increased number of macrophages and overall tissue cellularity (p < .05). No significant relationship was observed between mediator production and clinical symptoms. We conclude that overall cellularity, specifically macrophages, in the periprosthetic capsule may lead to TNF-alpha production but that cytokine production by periprosthetic tissues alone is not a predictor of clinical symptomatology in patients with silicone breast prostheses.

Adult↗
PubMedDate not supplied

Gluconeogenic enzymes in defined structures of developing rat nephron.

Three gluconeogenic enzymes, P-pyruvate carboxykinase (PPCK), fructose-1-6 bisphosphatase (FBPase), and glucose-6-phosphatase (G6Pase) were measured in identified structures of rat nephron from 2 days before birth to maturity. In the proximal convoluted tubule, the three enzymes increased from the earliest age assayed to +14 days (PPCK, 7-fold, FBPase, 2-fold and G6Pase, 50-fold). Among the 7 defined structures that were analyzed, highest levels at all ages were in the proximal convoluted tubule with almost no activity in the distal convoluted tubule. All three enzymes had negligible activity in the neogenic zone and mesenchyme. Supported by grants from the Public Health Service (HD 03891 and NS-05221) and the American Cancer Society (P-78).

Aging↗