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Biomedical subjects

D Clark

Publications and source records attributed to D Clark.

At least 235 records · Page 13Linked to original sources
PubMed1991

Contradictions in the development of new hospices: a case study.

Despite a decade of concern about the 'mushrooming' of new hospice developments within the British Isles, we remain remarkably ignorant about the processes which lead to the initiation of new hospice projects and the factors which affect their progress. Three inter-related issues appear important: (1) policy and resource implications; (2) changing models of hospice care; (3) 'community' factors. This paper explores the interconnections between these, using a case study approach and describes in detail the efforts of a single local voluntary group to establish a programme of community care for dying people. It shows that: (1) local 'communities' are likely to make continued demands for hospice type care, despite official scepticism about proliferation; but also that these communities should not be seen as homogeneous in their aspirations and demands; (2) new models of community care will interact with wider policy changes in the NHS and Social Services to raise questions about how terminal care services can be further developed; (3) shifts away from traditional in-patient models of care are likely to high-light divisions between 'lay' and 'professional' groups in their perceptions of how services can be delivered.

Community Participation↗
PubMed1991

Disseminated pneumocystis carinii infection in AIDS.

Eight patients with AIDS and Pneumocystis carinii infection were studied. Protean manifestations were a feature not untypical of disseminated pneumocystosis. Aerosolised pentamidine as prophylaxis against P carinii pneumonia was ineffective at suppressing dissemination. The knowledge that extrapulmonary infection can occur has implications for the detection and treatment of, and prophylaxis against, P carinii infection. The survival of patients with disseminated pneumocystosis is particularly poor, and may be due to a lack of clinical awareness and consequent delay in diagnosis.

Acquired Immunodeficiency Syndrome↗
PubMed1991

MR imaging in hydatid disease.

Hydatid cysts may develop anywhere in the body as a result of the presence of a viable parasite (Echinococcus granulosus). Depending on the condition of the parasite, the host reaction, and therapy, the hydatid cyst will degenerate and may eventually collapse, leaving an area of calcification in the host tissue. The purpose of this pictorial essay is to demonstrate the use of MR imaging in the diagnosis of the various stages of hydatid disease and in monitoring response to therapy.

Albendazole↗
PubMed1991

Treatment of antenatal myasthenia gravis.

Maternal myasthenia gravis has been associated with the presence of neonatal myasthenia and sometimes fatal congenital anomalies. As a result, antenatal therapy directed at fetal sequelae may be indicated. We present the case of a pregnant myasthenic woman whose two previous pregnancies had ended in neonatal deaths from fetal deformations that were presumably due to maternal myasthenia. Serial plasmaphereses and oral prednisone therapy were used in an attempt to depress maternal anti-acetylcholine receptor antibody titers. As anti-acetylcholine receptor antibody titers fell, fetal breathing movements became apparent by ultrasound, and as these titers rose, no fetal breathing movements were apparent. Our patient delivered an infant with transient neonatal myasthenia but normal pulmonary development and no deformations. We suggest that the therapy given may have improved the outcome of this pregnancy compared with her two previous pregnancies.

Administration, Oral↗
PubMed1990

Genomic organization of the human multidrug resistance (MDR1) gene and origin of P-glycoproteins.

The MDR1 gene, responsible for multidrug resistance in human cells, encodes a broad specificity efflux pump (P-glycoprotein). P-glycoprotein consists of two similar halves, each half including a hydrophobic transmembrane region and a nucleotide-binding domain. On the basis of sequence homology between the N-terminal and C-terminal halves of P-glycoprotein, we have previously suggested that this gene arose by duplication of a primordial gene. We have now determined the complete intron/exon structure of the MDR1 gene by direct sequencing of cosmid clones and enzymatic amplification of genomic DNA segments. The MDR1 gene includes 28 introns, 26 of which interrupt the protein-coding sequence. Although both halves of the protein-coding sequence are composed of approximately the same number of exons, only two intron pairs, both within the nucleotide-binding domains, are located at conserved positions in the two halves of the protein. The other introns occur at different locations in the two halves of the protein and in most cases interrupt the coding sequence at different positions relative to the open reading frame. These results suggest that the P-glycoprotein arose by fusion of genes for two related but independently evolved proteins rather than by internal duplication.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Aggressive jejunal lymphoma of large granular lymphocytes. Immunohistochemical, ultrastructural, molecular, and DNA content analysis.

An unusual large cell lymphoma of the proximal jejunum with large granular lymphocyte (LGL) morphologic characteristics and T-helper/inducer cell phenotype is described. Although the cells strongly expressed Leu-7 (HNK-1), studies with antibodies directed against the more specific natural killer (NK) antigens, CD16 (Leu-11) and Leu-19, were negative. Ultrastructural analysis of the neoplastic cells demonstrated substantial numbers of electron-dense granules and rare parallel tubular arrays. Clonal rearrangement of the T-cell receptor beta chain gene and germline configuration of the immunoglobulin heavy chain gene confirmed the T-cell origin of the neoplastic cells. This lymphoma pursued an aggressive clinical course, with rapid dissemination to the lungs and central nervous system. DNA content analysis indicated that a similar DNA aneuploid population was present in the jejunal primary and lung tissue at recurrence. There was no evidence of nodal, peripheral blood, splenic, or bone marrow involvement. Morphologic and functional similarities between the lymphoid tissues of the gastrointestinal tract and lung have previously prompted a classification of the immune system into distinct peripheral somatic and mucosal components. Based on the distribution and migratory properties of the tumor cells in this case, the authors propose that this lymphoma arose from a minor mucosa-associated LGL subset that may be unrelated to circulating LGLs. In addition, these observations emphasize that prominent granulated cytomorphologic features may be seen in neoplastic disorders with the T-helper/inducer phenotype, as well as in the more widely recognized lymphoproliferative disorders of NK and cytotoxic/suppressor cell types.

Aged↗
PubMed1990

Cardiovascular and symptomatic reduction effects of alprazolam and imipramine in patients with panic disorder: results of a double-blind, placebo-controlled trial.

Seventy-nine patients with panic disorder were randomized to an 8-week double-blind treatment with alprazolam, imipramine, or placebo. Patients kept daily records of panic attacks, activity, anxiety, sleep, and medication use. Weekly measures of anxiety, depression, somatic symptoms, fears, avoidance, disability, and improvement were obtained. All patients underwent a symptom-limited exercise treadmill and other cardiovascular measures. By physician and patient global assessment, patients receiving alprazolam or imipramine were significantly better than patients on placebo. The alprazolam effects were apparent by week 1; the imipramine effects by week 4. All groups showed significant reductions in anxiety, depression, somatic measures, and panic attack frequency. At 8 weeks, patients in the alprazolam group reported significantly less fear than patients in the other two groups. Subjects in the imipramine group showed a significant increase in heart rate and blood pressure.

Adult↗
PubMed1990

Identification and catabolic activity of well-derived gasoline-degrading bacteria from a contaminated aquifer.

Approximately 300 gasoline-degrading bacteria were isolated from well water and core material from a shallow coastal aquifer contaminated with unleaded gasoline. Identification of 244 isolates revealed four genera: Pseudomonas, Alcaligenes, Nocardia, and Micrococcus, with pseudomonads making up 86.9% of bacteria identified. A total of 297 isolates was sorted into 111 catabolic groups on the basis of aerobic growth responses on 15 gasoline hydrocarbons. Each test hydrocarbon was degraded by at least one isolate. Toluene, p-xylene, ethylbenzene, and 1,2,4-trimethylbenzene were most frequently utilized as growth substrates, whereas cyclic and branched alkanes were least utilized. Most isolates were able to grow on 2 or 3 different hydrocarbons, and nearly 75% utilized toluene as a sole source of carbon and energy. Isolates were remarkably specific for hydrocarbon usage, often catabolizing only one of several closely related compounds. A subset of 220 isolates was sorted into 51 groups by polyacrylamide gel electrophoresis. Pseudomonas aeruginosa was partitioned into 16 protein-banding groups (i.e., subspecies) whose catabolic activities were largely restricted to substituted aromatics. Different members of subspecies groups defined by protein-banding pattern analysis often exhibited different growth responses on the same hydrocarbon, implying marked strain diversity. The catabolic activities of well-derived, gasoline-degrading bacteria associated with this contaminated aquifer are consonant with in situ adaptation at the site.

Bacteria, Aerobic↗
PubMed1990

Expression of the functional cone phototransduction cascade in retinoblastoma.

Retinoblastoma is a malignant intraocular tumor that primarily affects small children. These tumors are primitive neuroectodermal malignancies, however some of them show morphologic evidence of differentiation into photoreceptors. Phototransduction cascades are a series of biochemical reactions that convert a photon of light into a neural impulse in rods and cones. The components of these cascades are uniquely expressed in photoreceptors and, although functionally similar, distinct components of these cascades are expressed in rods and cones. Using HPLC anion exchange chromatography, Western blot analysis, and specific monoclonal and polyclonal antibodies, we found that the cone but not the rod cGMP phosphodiesterase is functionally expressed in all six primary retinoblastomas examined and in three continuous retinoblastoma cell lines. Morphologic evidence of differentiation did not correlate with the expression of the enzyme. Furthermore, GTP analogues could activate the phosphodiesterase activity suggesting that an intact phototransduction cascade is present in the tumors. The presence of the cone phototransduction cascade in retinoblastoma confirms that this tumor has biochemically differentiated along the cone cell lineage.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Mesenteric vein thrombosis, non-invasive diagnosis and follow-up (US + MRI), and non-invasive therapy by streptokinase and anticoagulants.

We report on the case of a young lady on oral contraceptives for only 1 month who experienced severe central abdominal pain of a progressive nature. Mesenteric vein thrombosis was diagnosed by ultrasound and confirmed by magnetic resonance imaging. The patient was treated initially with streptokinase followed by heparin and warfarin with subjective improvement, and gradual disappearance of the thrombus was observed on ultrasound and magnetic resonance imaging. In this report we wish to emphasize the feasibility of the early diagnosis of mesenteric vein thrombosis by ultrasound and magnetic resonance imaging, and the effectiveness of early thrombolytic therapy without the need for surgical intervention.

Adult↗
PubMed1990

Mineralization of S from dibenzothiophene, dibenzothiophene sulphone, and benzene sulphonic acid by soil isolates.

The presence of substantial levels of organic S in coal is a major source of air pollution, and considerable efforts are being made to devise a cost-effective way of removing this form of sulphur. One method is to develop naturally occurring bacteria capable of heterocyclic organic S degradation and S mineralization. In this study, fourteen isolates capable of dibenzothiophene (DBT), dibenzothiophene sulphone (DBTS) or benzene sulphonic acid (BSA) decomposition were obtained from samples collected from an abandoned strip mine. The degradation of DBT varied from 4.4 to 91% and the mineralization of S as sulphate was less than or equal to 1.5%. Higher rates of DBTS decomposition were determined (94.9 to 97.7%) and S mineralization varied from 21.8 to 30.8%. The extent of BSA degradation could not be determined, but 57.8 to 71.1% of the S was mineralized as sulphate. All of the soil isolates possessed a single plasmid 20 to 23 kb in size.

Air Pollution↗
PubMed1990

Physician referrals from a rural family practice residency clinic: a pilot study.

Primary care physicians see large volumes of unscreened patients in the office setting, and referral to more specialized colleagues is always an option. Discretionary factors may play an important role in the referral decision. In this study, three family physicians retrospectively rated 410 referrals from a rural academic practice for the need for referral based on lack of specialized skills or knowledge by family physicians and the probability of adverse patient outcome. Referrals relating to cancer and pregnancy were rated as less discretionary than other referrals. Specialties receiving the highest proportion of mandatory or probably mandatory referrals were ophthalmology and cardiology. Half of all referrals studied were considered to be elective or possibly elective, although 97 percent of referrals to dermatology were considered elective or probably elective. These findings support the hypothesis that there is considerable clinical discretion in a large proportion of referrals. Hence, imposition of specific criteria for referral in primary care practice (thereby limiting discretion in initiating a referral) could significantly decrease the number of referrals, and consequently decrease the income of subspecialists and tertiary care centers.

Adult↗