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Biomedical subjects

J Anderson

Publications and source records attributed to J Anderson.

At least 469 records · Page 26Linked to original sources
PubMed1992

Modification of the percutaneous approach to peritoneal dialysis catheter placement under peritoneoscopic visualization: clinical results in 78 patients.

The placement of percutaneous peritoneal dialysis catheters under direct peritoneoscopic visualization is a relatively new technique for establishing peritoneal dialysis access. In this study, in which a modification of the Seldinger technique was used to facilitate the placement of the peritoneoscope, the experience with 82 consecutive catheterization procedures in 78 patients is reported. In 2 (2.4%) of 82 catheterization procedures, we were unable to enter the peritoneal cavity but experienced no other complications unique to the percutaneous approach. Of the 80 successful catheterization procedures, 76 represented first-time catheter placement and constituted a population subjected to life-table analysis examining catheter survival rates, the time to first cutaneous exit site or s.c. tunnel infection, and the time to first episode of peritonitis. After a follow-up period of 50.1 patient yr, 11 catheters were lost because of catheter dysfunction. Other clinical complications included peritoneal fluid leaks at the cutaneous exit site in 11 instances (0.22/patient yr), cutaneous exit site infection in 7 instances (0.14/patient yr), s.c. tunnel infection in 2 instances (0.04/patient yr), and 34 episodes of peritonitis (0.68/patient yr). The results of this study demonstrate that the suggested modification of the percutaneous placement of peritoneal dialysis catheters, under peritoneoscopic visualization, is a viable method for establishing peritoneal access.

Adult↗
PubMed1992

Relationship of [3H]Ara-C incorporation and response to therapy with high-dose Ara-C in AML patients: a Leukemia Intergroup study.

Pretherapy bone marrow (BM) aspirates of 143 patients with acute myeloid leukemia (AML) were incubated simultaneously with bromodeoxyuridine (BrdU) and tritiated cytosine arabinoside ([3H]Ara-C) to determine the labeling index (LI) and extent of [3H]Ara-C incorporation. Of 143 AML patients, 121 received high-dose Ara-C (HDAra-C) as a single agent for induction therapy (55 newly diagnosed, 66 in first relapse), whereas 22 received HDAra-C plus mAMSA. The data demonstrate that a subset of patients who will fail HDAra-C remission induction therapy because of drug-resistant disease can be prospectively identified on the basis of the low amount of Ara-C incorporated by their leukemia cells.

Acute Disease↗
PubMed1992

Age-related differences in vascular effects of pentoxifylline in isolated perfused ferret lungs.

We have determined the magnitude and sites of action of pentoxifylline (PTX), a methylxanthine derivative, in the adult and 3- to 4-week old ferret pulmonary circulation. Lungs of 8 ferrets, four 3- to 4-week-old and 4 adult, were isolated and perfused with blood. During perfusion, blood flow was kept constant, as were airway and left atrial pressures (6 and 8 cm H2O respectively, zone 3 conditions). In all lungs, pulmonary artery pressure was measured continuously and the circulation was partitioned into arteries, microvessels and veins, by measurement of pressures in 20-50 microns diameter subpleural arterioles and venules using the micropipette-servonulling method. Pressures were obtained in each lung during baseline, after vasoconstriction with hypoxia, and again after the infusion of PTX, 20 mg/kg, during hypoxia. We found that with hypoxia, total vascular resistance increased by approximately 90% in both adult and neonatal lungs; arterial and venous resistances increased by 100-180% in both age groups, with little change in microvascular resistance. PTX resulted in a significant decrease in total vascular resistance, due to a decrease in resistance in both arteries and veins. The decrease in resistance with PTX was greater in adult lungs (of the increase in resistance induced by hypoxia, 80% was eliminated by PTX) than in 3- to 4-week old lungs (51% elimination of tone induced by hypoxia). This difference was mainly due to a smaller reduction in arterial resistance with PTX in 3- to 4-week-old lungs. We conclude that PTX is a powerful pulmonary vasodilator in ferrets and that its effectiveness as a vasodilator depends on the age of the animal, the older animal showing greater responsiveness.

Aging↗
PubMed1992

Laboratory and clinical studies of biochemical modulation by hydroxyurea.

Hydroxyurea is a potent inhibitor of the enzyme ribonucleotide reductase. Due to its effects on cellular deoxyribonucleotide pools, hydroxyurea can modulate the activity of several pyrimidine and purine antimetabolites. As an inhibitor of DNA repair, it can potentially interact with DNA-damaging agents such as alkylating agents or inhibitors of topoisomerase II. Both cytokinetic and biochemical interactions occur between hydroxyurea and cytarabine (ara-C), which account for their synergistic cytotoxicity. Inhibition of ribonucleotide reductase by hydroxyurea depletes cellular deoxycytidine triphosphate pools, thereby enhancing ara-C uptake and phosphorylation to ara-C triphosphate. In a phase II clinical trial, the combination of hydroxyurea and ara-C produced a 43% response rate in patients with refractory malignant lymphoma. Studies in murine leukemia models have demonstrated therapeutic synergy when hydroxyurea is combined with fluoropyrimidines. High levels of deoxyuridine monophosphate that have been associated with resistance to 5-fluorouracil can be suppressed by hydroxyurea, leading to greater inhibition of thymidylate synthase. Despite the strong biochemical rationale for the use of hydroxyurea and 5-fluorouracil in combination, few clinical trials have been conducted thus far. Antimetabolites and topoisomerase II inhibitors have also been shown to be synergistic in vitro. Hydroxyurea has been shown to enhance the formation of DNA strand breaks produced by amsacrine and to produce synergistic cytotoxicity with etoposide. A phase I clinical trial of these drugs has demonstrated bone marrow suppression to be the major toxicity of the combination. In summary, hydroxyurea has been shown to undergo cytokinetic and biochemical interactions with a number of established antitumor agents. Clinical trials of hydroxyurea in combination with these agents have identified doses and schedules of administration that produce acceptable levels of clinical toxicity and appear feasible for further testing.

Animals↗
PubMed1991

Auditing audits: the method of Oxfordshire Medical Audit Advisory Group.

OBJECTIVES: To develop a systematic method for both summative and formative audit of practice audits, and to use the method to review Oxfordshire practice audits and to plan improvement. DESIGN: Development of a coding system for the audit cycle subsequently used prospectively to assess audits reported to medical audit advisory group coordinators on practice visits. SETTING: All 85 general practices in Oxfordshire, of which 80 were visited by Oxfordshire Medical Audit Advisory Group coordinators. MAIN OUTCOME MEASURES: Satisfaction of criteria for different levels of audit (full, partial, potential, planning or no audit) according to coding scores for practice audits. RESULTS: 46 (58%) practices were classified as doing audit, the remainder doing no audit or only collecting data for family health services authority returns. Of audits being undertaken, 55/102 (54%) included planning care or the setting of targets. CONCLUSIONS: The coding system offers the prospect of formative assessment for practices to help them improve their audits, and summative assessment for the family health services authority to satisfy the needs for professional accountability. Its use in Oxfordshire disclosed considerable deficiencies in the process of practice audit. IMPLICATIONS AND ACTION: Practices in Oxfordshire should improve their audits. The advisory groups target to March 1992 is for 50% of practices to be doing full or partial and 25% potential audit and half of the remainder planning audit. Practices are encouraged to include in their audit implementing change, planning care, and agreeing criteria for further assessment.

England↗
PubMed1991

Prevention of perinatal transmission of hepatitis B virus (HBV): a comparison of two prophylactic schedules.

Perinatal transmission of hepatitis B virus (HBV) from HBsAg carrier mothers who were HBeAg+, antiHBe+, or negative for both HBe markers, was interrupted using either 4 doses of vaccine, or one dose of hepatitis B immunoglobulin (HBIG) at birth, combined with 4 doses of vaccine. In those infants who received HBIG at birth, the antiHBs titre was significantly higher at 1 and 2 months old, but at 6, 9, and 18 months old, there was no significant difference. Among the infants of carrier mothers who did not display HBeAg (i.e., were antiHBe+, or negative for both HBe markers), a transient subclinical infection would have been expected in around 10% had there been no intervention. No evidence of such infection was detected, and no difference in outcome was found between the two treatment groups. Amongst infants born to HBeAg+ carrier mothers, infection occurred in 1 out of 8 who had received HBIG and vaccine, and in 3 of 8 who had received vaccine only. The difference in outcome was not statistically significant, but the numbers analysed were small. The infections which occurred in spite of prophylaxis may be attributable to in utero infection, poor response to vaccine by the infant, or to the mother having a particularly high HBV-DNA level. HBIG given at birth to infants of HBeAg+ carrier mothers may enhance the protection of infants who are destined to be poor responders to vaccine.

Carrier State↗
PubMed1991

Effect of edema on segmental vascular resistance in isolated perfused rat lungs.

We have determined the effect of hydrostatic edema on total and segmental vascular resistances in the rat lung. Lungs of 12 adult rats, body weight 515 +/- 42 g, were isolated and perfused with blood. To investigate the role of vasoactivity on edema effects, we studied two groups of lungs; group I (n = 6) were untreated and group II (n = 6) were treated with papaverine hydrochloride to paralyze the vasculature. Initially blood flow was adjusted to keep pulmonary artery pressure approximately 15 cmH2O, left atrial and airway pressures being 8 and 7 cmH2O, respectively, and then kept unchanged thereafter (18 +/- 3 ml/kg/min). Hydrostatic edema was induced by raising venous pressure and pulmonary artery pressure measured continuously. In 4 lungs from each group, during baseline and after the development of severe edema, we partitioned the pulmonary circulation into arteries, microvessels, and veins by measuring pressures in 20-50 microns diameter subpleural arterioles and venules with the micropipette-Servonull method. Baseline total vascular resistance was similar in the two groups. Interstitial and early alveolar edema did not affect pulmonary vascular pressures. With severe edema (W/D ratio: 17 +/- 2), pressures in pulmonary artery and arterioles increased significantly in both groups; venular pressures did not change. Total resistance increased by 250% in group I and by 224% in group II lungs. Arterial resistance increased 3-5-fold in both groups, as did microvascular resistance. Venous resistances also increased in both groups, although to a lesser extent. The increase in total and segmental vascular resistances was not significantly different in the two groups of lungs. We conclude that in isolated rat lungs only severe edema results in an increase in total vascular resistance, mainly due to an increase in arterial and microvascular resistances, with a smaller increase in venous resistance. This appears to be a mechanical effect of edema on the vasculature and not a result of active vasomotion.

Animals↗
PubMed1991

Vasoconstrictor response to prostacyclin in rabbit pulmonary circulation.

We have determined the effect of prostacyclin (PGI2) on segmental vascular resistance in rabbit lungs. Lungs of 26 rabbits were isolated and perfused with blood; 16 adult, greater than 6 months old, five juvenile, 6-8 week old and five neonatal, 2-3-week old. Six of the adult lungs were pretreated with indomethacin to block cyclooxygenase, prior to infusion of PGI2. In all lungs, flow was adjusted initially to keep pulmonary artery pressure approximately 20 cmH2O, left atrial and airway pressures being 8 and 6 cmH2O, respectively (zone 3), and then kept constant. We measured pulmonary artery pressure continuously and in the 10 untreated adult lungs, in which a vasoconstrictor response to PGI2 was obtained, we also measured pressures in 20-50 microns diameter subpleural arterioles and venules by the micropipette-servonulling method. We found that in juvenile and neonatal rabbit lungs, PGI2 did not change total vascular resistance significantly but in untreated adult lungs, it caused a significant increase in total vascular resistance only after a dose of 10 micrograms/kg. This age-related difference in vasoconstrictor response to PGI2 was not related to baseline total vascular resistance in the three groups of lungs. In adult lungs, vasoconstriction occurred mainly in arteries with a small effect in veins. Circulating levels of thromboxane B2, leukotriene C4, and 6-keto-PGF1 alpha increased following PGI2 infusion in adult lungs, whereas in neonatal lungs, only 6-keto-PGF1 alpha increased significantly. Indomethacin pretreatment completely abolished the vasoconstrictor response to PGI2. We conclude that PGI2-induced vasoconstriction is age and dose dependent in isolated rabbit lungs and that a cyclooxygenase product, such as thromboxane A2, may play a role in mediating the vasoconstriction.

Aging↗