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Biomedical subjects

C Eng

Publications and source records attributed to C Eng.

262 records · Page 15Linked to original sources
PubMed1980

Breath concentration as an index of the health risk from benzene. Studies on the accumulation and clearance of inhaled benzene.

Human subjects were exposed to known concentrations of benzene in air for single and repeated daily periods. The breath concentrations measured repeated exposures approached a maximum after 3 d, and this phenomenon indicated that the tissues were approaching saturation under the experimental conditions. The breath concentrations measured after exposure indicated an initial rapid clearance of benzene with a half-time of 2.6 h, followed by a slower phase with a half-time of 24 h. The decay in breath concentration after prolonged occupational exposure appeared to be slower; the difference between the laboratory and industrial studies was, however, not significant. The hygienic significance of these results was discussed, and it was recommended that control measures be employed when a morning breath concentration exceeds 10 ppb.

Atmosphere Exposure Chambers↗
PubMed1976

Serum quinidine levels after chronic administration of four different quinidine formulations.

The serum levels produced by four different quinidine formulations have been studied. The relative bioavailability of the formulations was demonstrated as were the mean peak serum levels and their timing in relation to dosage. From the data obtained, the biological half-lives were measured and the apparent volume of distribution and total body clearance were calculated for each formulation. The generic tablets of quinidine monosulphate from five different manufacturers were not significantly different from each other in any respect and produced the expected peak and trough serum level curves. The serum level curves resulting from administration of quinidine polygalacturonate (Cardioquin) were not significantly different from those resulting from the generic tablets, and this formulation may be regarded as therapeutically equivalent to the generic formulations. Both sustained-release formulations of quinidine bisulphate, Durettes and Kiditard (given at the same dosage) were shown to offer a means whereby, with simple twice-daily dosage, quinidine maintenance treatment may be continued with the confidence that the serum levels may be maintained throughout each 24-hour period without peaks into the toxic levels and troughs into the levels of no effect.

Adult↗
PubMedDate not supplied

The effect of coronary arterial pressure on myocardial distensibility. Absence of a "garden hose" effect during in-vivo conditions.

The effect of the coronary perfusion pressure on myocardial distensibility was studied in 11 open-chest dogs. The left anterior descending coronary artery was cannulated, and coronary perfusion pressure and blood flow were measured. Regional myocardial segment length was measured using sonomicrometers. The temporal relationship between the phasic coronary pressure fall and change in myocardial segment length was analyzed during the early phase of coronary occlusion. Diastolic myocardial segment length was completely unaffected by the substantial fall in coronary pressure over a period of 9.3 +/- 0.8 s (20 +/- 2 heart beats). During this period, coronary pressure fell from 98 +/- 7 to 28 +/- 2 mm Hg. Subsequently, diastolic segment length increased, presumably due to ischemia rather than to a delayed compliance change. In order to differentiate between a possible long-time constant for coupling of the intravascular pressure to myocardial compliance versus a primary ischemic effect, regional cardiac contraction was abolished by an intracoronary potassium chloride infusion in three dogs. Coronary occlusion during regional cardioplegia produced no further segment length changes for a 1-min period, effectively excluding viscoelastic coupling time constants of up to 1 min. From these results we conclude that the coronary distending pressure does not contribute to passive myocardial properties over the physiological perfusion pressure range, and that the "garden hose" effect is not operative for the in vivo working heart.

Animals↗
PubMedDate not supplied

Rapid mutation scanning of genes associated with familial cancer syndromes using denaturing high-performance liquid chromatography.

Germline mutations in tumor suppressor genes, or less frequently oncogenes, have been identified in up to 19 familial cancer syndromes including Li-Fraumeni syndrome, familial paraganglioma, familial adenomatous polyposis coli and breast and ovarian cancers. Multiple genes have been associated with some syndromes as approximately 26 genes have been linked to the development of these familial cancers. With this increased knowledge of the molecular determinants of familial cancer comes an equal expectation for efficient genetic screening programs. We have trialled denaturing high-performance liquid chromatography (dHPLC) as a tool for rapid germline mutation scanning of genes implicated in three familial cancer syndromes -- Cowden syndrome (PTEN mutation), multiple endocrine neoplasia type 2 (RET mutation) and von Hippel-Lindau disease (VHL mutation). Thirty-two mutations, including 21 in PTEN, 9 in RET plus a polymorphism, and 2 in VHL, were analyzed using the WAVE DNA fragment analysis system with 100% detection efficiency. In the case of the tumor suppressor gene PTEN, mutations were scattered along most of the gene. However, mutations in the RET proto-oncogene associated with multiple endocrine neoplasia type 2 were limited to specific clusters or "hot spots." The use of GC-clamped primers to scan for mutations scattered along PTEN exons was shown to greatly enhance the sensitivity of detection of mutant hetero- and homoduplex peaks at a single denaturation temperature compared to fragments generated using non--GC-clamped primers. Thus, when scanning tumor suppressor genes for germline mutation using dHPLC, the incorporation of appropriate GC-clamped primers will likely increase the efficiency of mutation detection.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Integrating acute and long-term care for high-cost populations.

The inadequacies of our fragmented acute and long-term care financing and delivery systems have been well recognized for many years. Yet over the past two decades only a very small number of "boutique" initiatives have been able to improve the financing and the delivery of care to chronically ill and disabled populations. These initiatives share most of the following characteristics: prepaid, risk-adjusted financing; integrated Medicare and Medicaid funding streams; a flexible array of acute and long-term benefits; well-organized, redesigned care delivery systems that tailor these benefits to individual need; a mission-driven philosophy; and considerable creativity in engaging government payers. The experience of these "boutiques" illustrates both the obstacles to, and the opportunity for, meaningful, widespread care delivery reform for vulnerable chronically ill populations.

Acute Disease↗
PubMedDate not supplied

Medical management of orbital subperiosteal abscess in children.

The traditional treatment of subperiosteal orbital abscess consists of surgical drainage and antibiotic therapy. We successfully treated with antibiotics alone nine children (age range 26 months to 12 years) with clinical signs and symptoms of orbital cellulitis and computerized tomographic (CT) evidence of subperiosteal abscess and contiguous ethmoid sinusitis. Two additional patients successfully treated with nonsurgical therapy were identified retrospectively. All patients were admitted to the pediatric service with normal vision. Their visual function was assessed twice daily during the early stages of their illness. All patients improved with intravenous antibiotic therapy. One additional patient required surgical drainage for persistent pain after 1 week of slow but steady clinical improvement. All other patients were clinically cured with medical therapy alone. Five of the medical "cures" had posttreatment CT, which documented the resolution. No patient had a recurrence. We conclude that orbital subperiosteal abscess, like some other abscesses located elsewhere, may be amenable to non-surgical treatment, or that these patients may have had a phlegmon rather than an abscess and the currently accepted CT criteria for diagnosis of a subperiosteal abscess may require modification. We recommend that children with a subperiosteal abscess from contiguous ethmoidal sinusitis who have no evidence of compromised optic nerve function be given a trial of intravenous antibiotic therapy prior to consideration of surgical drainage.

Abscess↗
PubMedDate not supplied

Familial Barrett esophagus and adenocarcinoma of the gastroesophageal junction.

Barrett esophagus was found in seven members of a single family. Two of these patients also had adenocarcinoma of the gastroesophageal junction. Among family members who did not have Barrett epithelium, one had esophageal ulcerations with dysplasia in squamous epithelium and another had an esophageal stricture. The pattern of involvement suggests autosomal dominant inheritance of Barrett esophagus and/or gastroesophageal reflux disease in this family, with a strong predisposition for adenocarcinoma of the esophagus.

Adenocarcinoma↗
PubMedDate not supplied

Endothelin-3 gene mutations in isolated and syndromic Hirschsprung disease.

Hirschsprung disease (HSCR, aganglionic megacolon) is a frequent congenital malformation regarded as a multigenic neurocristopathy. Four susceptibility genes have recently been identified in HSCR, namely the RET proto-oncogene, the glial cell line-derived neurotrophic factor (GDNF), the endothelin B receptor (EDNRB) and the endothelin-3 genes (EDN3). Homozygosity for EDN3 mutations has been previously shown to cause the Shah-Waardenburg syndrome, a combination of HSCR with features of the Waardenburg syndrome. Here, we report on heterozygous EDN3 missense mutations in isolatec HSCR. The present data give further support to the role of the endothelin signaling pathway in the development of neural crest-derived enteric neurons. They also suggest the possibility that either recessive or weakly penetrant dominant alleles could occur at the EDN3 locus, depending on the nature of the mutation.

Endothelin-3↗