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Biomedical subjects

J Richardson

Publications and source records attributed to J Richardson.

At least 271 records · Page 15Linked to original sources
PubMed1990

Indirect choroidal ruptures: aetiological factors, patterns of ocular damage, and final visual outcome.

Indirect choroidal ruptures result from blunt ocular trauma and have a pathognomonic fundal appearance. We analysed a group of 30 patients with indirect choroidal ruptures with specific reference to the circumstances of the injury, the pattern of ocular damage, the cause of any visual loss, and the final visual outcome. Using this analysis we deduce a pathogenetic explanation for the characteristic fundus signs in patients with indirect choroidal ruptures. The majority of cases were young males injured during sport or by an assault, a minority were injured at work. Diffuse nonfocal impact injuries due to punches were associated with ruptures concentric with and adjacent to the optic disc. Focal impact injuries, due to projectiles, showed more extensive ocular damage. Seventeen of 30 patients regained 6/12 vision after injury. Injuries due to projectiles and temporally situated ruptures were associated with a poorer visual outcome than others. Macular damage was the commonest cause of visual loss, principally due to pigmentary maculopathy, traumatic inner retinal damage, and choroidal neovascular membranes rather than direct focal damage by the rupture.

Adolescent↗
PubMed1990

Frontal bone epidermoid--a rare cause of proptosis.

Frontal bone epidermoid is a rare condition which may present with proptosis, extraocular muscle imbalance, or loss of vision. Clinically and on plain radiographs an epidermoid may be confused with commoner conditions such as frontal mucocoele. However, the characteristic CT scan appearance, which shows a bone cyst with similar density to brain tissue, should lead to an accurate diagnosis and appropriate surgical management.

Bone Cysts↗
PubMed1990

Tobacco excise and declining tobacco consumption: the case of Papua New Guinea.

Excise elasticities of demand for non-cigarette tobacco and cigarettes were calculated for Papua New Guinea for the 14 years 1973-86. Respectively, these were -0.50 and -0.71. This means that 10 percent increases in cigarette and non-cigarette tobacco excise are associated with an estimated 7.1 percent fall in demand for cigarettes and a 5 percent decrease in the demand for tobacco. As tax (excise) elasticities would normally be significantly smaller than price elasticities, these results imply that the consumption of cigarettes and tobacco in Papua New Guinea are more responsive to prices than in the United States and other Western countries. The level of excise is therefore an important and practical instrument for the control of consumption. These elasticities appear to be the first reported for a developing country. It is suggested that if they are indicative of consumer behavior in lower income countries then increasing tobacco and cigarette excise should be considered as an important strategy for the control of smoking in these countries which, because of their large populations, are huge markets for tobacco products and thus major targets for tobacco control measures.

Developing Countries↗
PubMed1990

Materiel management in the operating room: a case study.

The hospital continues to be pleased with the progress of our material services program in all areas, but especially surgery. It took a few simple, basic methods, such as exchange carts and inventory control, mixed them with people who actually care about doing a good job, and the whole program moved forward dramatically. People, both in materiel services and surgery, have accomplished a tremendous amount in the past two years. They have made, and will continue to improve, an already excellent program.

Florida↗
PubMed1990

Gonadotropin hormone releasing hormone agonists [GnRHA] and prevention of familial breast cancer.

The use of GnRHA to induce a "medical" oophorectomy may be a useful method of prevention of breast carcinoma. The addition of ERT and intermittent progestogen to the GnRHA would be expected to prevent the adverse effects of estrogen deprivation, and still provide a significant reduction in breast cancer risk. Evaluation of the regimen in a high risk group such as sisters or daughters of index cases of early onset breast cancer is justifiable.

Adult↗
PubMed1989

A vitreoretinal service.

Many serious disorders that threaten eyesight can now be treated with vitreoretinal surgery. As there was no regional facility for this treatment a service was developed to provide it. Among the first 100 patients treated over half had diabetic vitreoretinal disease. The remainder had ocular trauma (15), non-diabetic vasculopathy (10), rhegmatogenous retinal detachment (10), and miscellaneous disorders including diagnostic procedures (14). Sight was improved in most cases, 27 diabetic and 21 non-diabetic patients regaining navigating vision. Few patients were made worse: one only of the 49 non-diabetic patients and 12 of the 51 diabetic patients, and none whose vision was better than the ability to count fingers before operation. The many indications for this procedure, the size of the population that could benefit (an estimated minimum of 3800 operations per year in the United Kingdom in patients with diabetes alone), and the great potential benefit of the procedure all suggest the need for regional services. These would be cost effective in preventing blindness.

Adolescent↗
PubMed1989

Role of acidic intracellular compartments in the biosynthesis of Dictyostelium lysosomal enzymes. The weak bases ammonium chloride and chloroquine differentially affect proteolytic processing and sorting.

Radiolabel pulse-chase and subcellular fractionation procedures were used to analyze the transport, proteolytic processing, and sorting of two lysosomal enzymes in Dictyostelium discoideum cells treated with the weak bases ammonium chloride and chloroquine. Dictyostelium lacks detectable cation-independent mannose-6-phosphate receptors and represents an excellent system to investigate alternative mechanisms for lysosomal enzyme targeting. Exposure of growing cells to ammonium chloride, which increased the pH in intracellular vacuoles from 5.4 to 5.8-6.1, slowed but did not prevent the proteolytic processing and correct localization of pulse-radiolabeled precursors to the lysosomal enzymes alpha-mannosidase and beta-glucosidase. Additionally, ammonium chloride did not affect transport of the enzymes to the Golgi complex, as they acquired resistance to the enzyme endoglycosidase H at the same rate as in control cells. When the pH of lysosomal and endosomal organelles was raised to 6.4 with higher concentrations of ammonium chloride, the percentage of secreted (apparently mis-sorted) precursor polypeptides increased slightly, but proteolytic processing of intermediate forms of lysosomal enzymes to mature forms was greatly reduced. The intermediate and mature forms of alpha-mannosidase and beta-glucosidase did, however, accumulate intracellularly in vesicles similar in density to lysosomes. In contrast, in cells exposed to low concentrations of chloroquine the intravacuolar pH increased only slightly (to 5.7); however, enzymes were inefficiently processed and, instead, rapidly secreted as precursor molecules. Experiments involving the addition of chloroquine at various times during the chase of pulse-radiolabeled cells demonstrated that this weak base acted on a distal Golgi or prelysosomal compartment to prevent the normal sorting of lysosomal enzymes. These results suggest that although acidic endosomal/lysosomal compartments may be important for the complete proteolytic processing of lysosomal enzymes in Dictyostelium, low pH is not essential for the proper targeting of precursor polypeptides. Furthermore, certain amines may induce mis-sorting of these enzymes by pH-independent mechanisms.

Acetylglucosaminidase↗
PubMed1989

Small round cell neoplasm of jaw in a patient with medulloblastoma.

A 24-year-old woman presented with a painful mandibular swelling 6 months after multimodality treatment for a cerebellar medulloblastoma. The tumor was microscopically identical to the cranial neoplasm and a part of widespread dissemination as determined by ancillary studies. Previous concepts of the nonmetastasizing nature of intracranial neuroectodermal neoplasms have been modified by studies on treated cases, surgery being considered a virtual prerequisite for this occurrence. Extracranial neoplastic development of a PNET of CNS origin must be considered in disease-free treated patients up to several years after initial therapy.

Adult↗
PubMed1989

A Dictyostelium discoideum mutant that missorts and oversecretes lysosomal enzyme precursors is defective in endocytosis.

A mutant strain of Dictyostelium discoideum, HMW570, oversecretes several lysosomal enzyme activities during growth. Using a radiolabel pulse-chase protocol, we followed the synthesis and secretion of two of these enzymes, alpha-mannosidase and beta-glucosidase. A few hours into the chase period, HMW570 had secreted 95% of its radiolabeled alpha-mannosidase and 86% of its radiolabeled beta-glucosidase as precursor polypeptides compared to the secretion of less than 10% of these forms from wild-type cells. Neither alpha-mannosidase nor beta-glucosidase in HMW570 were ever found in the lysosomal fractions of sucrose gradients consistent with HMW570 being defective in lysosomal enzyme targeting. Also, both alpha-mannosidase and beta-glucosidase precursors in the mutant strain were membrane associated as previously observed for wild-type precursors, indicating membrane association is not sufficient for lysosomal enzyme targeting. Hypersecretion of the alpha-mannosidase precursor by HMW570 was not accompanied by major alterations in N-linked oligosaccharides such as size, charge, and ratio of sulfate and phosphate esters. However, HMW570 was defective in endocytosis. A fluid phase marker, [3H]dextran, accumulated in the mutant at one-half of the rate of wild-type cells and to only one-half the normal concentration. Fractionation of cellular organelles on self-forming Percoll gradients revealed that the majority of the fluid-phase marker resided in compartments in mutant cells with a density characteristic of endosomes. In contrast, in wild-type cells [3H]dextran was predominantly located in vesicles with a density identical to secondary lysosomes. Furthermore, the residual lysosomal enzyme activity in the mutant accumulated in endosomal-like vesicles. Thus, the mutation in HMW570 may be in a gene required for both the generation of dense secondary lysosomes and the sorting of lysosomal hydrolases.

Cell Fractionation↗
PubMed1989

Comparison of preservation media and freezing conditions for storage of specimens of faeces.

To evaluate the long-term recoverability of bacterial enteropathogens, two freezing conditions (deep-freezing at -70 degrees C and liquid nitrogen) and three preservation media (Cary-Blair, Amies, and buffered glycerol-saline) were tested. These were compared with storage in containers with no preservation medium and refrigeration at 4 degrees C. At 4 degrees C, viability of organisms could not be consistently maintained beyond one month; Cary-Blair medium generally gave the best results and storage without preservation medium was the least efficient. Storage in liquid nitrogen and deep-freezing effectively preserved all organisms except Campylobacter jejuni for the entire period of study (12 months). There was no difference between the various preservation media, or between storage with or without medium. Storage in preservation medium was superior to storage without such supplement for C. jejuni. We conclude that most enteropathogens survive in faecal specimens for as long as 12 months when stored at very low temperatures (-70 degrees C) whether or not preservation media are used.

Cold Temperature↗
PubMed1989

Respiratory muscle performance in normal elderly subjects and patients with COPD.

We studied the reproducibility of tests of RM performance in normal elderly subjects and compared their performance with that of patients with COPD. The RM strength was measured as MIP and MEP. The RM endurance was measured using a two-minute incremental threshold loading test. The max load, the average Ppk as %MIP at max load and the Pmean at max load were taken as measures of respiratory muscle endurance. The MIP, but not MEP, was less in COPD patients than in normal subjects (p less than 0.05). There was a small increase in between visits, in MIP in the normal subjects. All measures of RM endurance were much lower in the COPD group than in the normal elderly (p less than 0.05). We conclude that (1) RM strength and endurance are reproducible in normal elderly subjects and patients with COPD, (2) that COPD subjects have decreased RM strength and endurance compared with normal elderly subjects, and (3) that in COPD subjects RM endurance is compromised more than RM strength.

Aged↗
PubMed1989

Bone metastases.

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Bone Neoplasms↗
PubMed1988

The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study.

The effects of natural hydrocarbons must be considered in order to develop a reliable plan for reducing ozone in the urban atmosphere. Trees can emit significant quantities of hydrocarbons to metropolitan areas such as Atlanta, and model calculations indicate that these natural emissions can significantly affect urban ozone levels. By neglecting these compounds, previous investigators may have overestimated the effectiveness of an ozone abatement strategy based on reducing anthropogenic hydrocarbons.

Air Pollutants↗
PubMed1988

Medical technology and its diffusion in Australia.

The author examines the Australian health care system by surveying the financing techniques, physical organization, and government activity. He explains the impact of the public and private sectors and comments on the effectiveness of current evaluation procedures. While the author believes that the system is relatively healthy and cost effective, he recognizes a need for more comprehensive and scientific oversight. Using regression analysis and focusing on the installation of medical technology in hospitals, the author attempts to determine the specific factors that influence technology diffusion. He concludes by stressing that further studies analyzing the actual use of specific technologies are vital.

Australia↗
PubMed1988

HTLV-1 infection in tropical spastic paraparesis: lymphocyte culture and serologic response.

All 17 patients with tropical spastic paraparesis (TSP) in a series seen in the United Kingdom have antibodies to the human T cell leukemia virus type 1 (HTLV-1). Cultured peripheral blood lymphocytes from these patients formed multinucleated giant cells and reacted with sera and monoclonal antibodies to HTLV-1 in a manner identical to adult T cell leukemia-lymphoma (ATLL) patient lymphocytes. Western blot analysis failed to reveal any marked difference in the antigens recognized by sera from TSP and ATLL patients. The sera from TSP patients, their asymptomatic relatives and ATLL patients were titrated using the following assays: enzyme-linked immunosorbent assays (ELISA), particle agglutination, antibody-dependent cell-mediated cytotoxicity, and pseudotype neutralization. There were significantly stronger serologic responses in the TSP patients than in their relatives or ATLL patients. High antibody titers in the presence of replicating virus often reflect the antigen load; however, these data are also consistent with the suggestion that neurologic damage in TSP may be immunologically mediated.

Adult↗