PubMed Health⌕ Search

Biomedical subjects

L Norris

Publications and source records attributed to L Norris.

At least 19 recordsLinked to original sources
PubMed2000

An in vitro assessment of the flow characteristics of spiral-ridged and smooth-walled JJ ureteric stents.

OBJECTIVE: To assess drainage through spiral-ridged and smooth-walled JJ ureteric stents (designed to ensure upper tract drainage) and thus determine whether drainage preferentially occurs around rather than through the spiral-ridged stent, promoting renal flow and potentially facilitating the passage of urinary stone fragments. Materials and methods A mechanical ureteric model was constructed to mimic the funnel characteristics of the renal pelvis. A motor pump was used to help simulate respiratory and skeletal movement, resulting in differential motion between the intraluminal stent and the surrounding ureteric wall. Tubes of varying internal diameters were used to simulate different sizes of ureter. Flow rates of standard 7 F smooth-walled stents were compared with 7 F spiral-ridged stents with and without occluded lumens, and with and without standardized excursions. RESULTS: Extraluminal flow (mean rates) with and without movements simulating respiratory excursions were significantly higher with the spiral stent for all stent diameters evaluated. All flow rates increased as the ureteric diameter increased. Total flow past the spiral stent was significantly greater than flow with the smooth-walled stent under all conditions tested. Flows measured around the spiral stent under conditions of excursion were the highest of all categories, 20-fold higher than in smooth-walled, closed, stationary stents. CONCLUSION: Spiral-ridged JJ stents provided substantially greater flow in this in vitro model. Extraluminal flow was markedly increased with the spiral-ridged configuration. The difference in flow rates was more pronounced at the smaller pseudo-ureteric tube diameters, simulating dimensions found in clinical practice. The flow rate also was increased when the central lumen remained open, and was greater still when there was dynamic excursion with respiratory movements.

Humans↗
PubMed1999

Perinatal aspects of inherited thrombophilia.

The identified main causes of inherited thrombophilia are deficiencies of antithrombin, protein C and protein S, activated protein C (APC) resistance and the factor V Leiden mutation, mutant factor II, and inherited hyperhomocysteinemia. In women from symptomatic families these defects may be associated with an increased risk of venous thrombosis in pregnancy and recurrent fetal loss. Inherited thrombophilia is common and appears to be a multigene disorder. The thrombotic risk would seem to be greatest in women with antithrombin deficiency and more than one thrombophilia defect. The abnormalities that are now recognized represent only part of the genetic predisposition to thrombosis. In assessing thrombotic risk in pregnancy, acquired risk factors as well as genetic predisposition should be considered. Increasing age, obesity, immobility, and delivery by cesarean section are major risk factors. Pregnancy should be planned, and each patient should be managed on an individual basis. In pregnancy, heparin is the anticoagulant of choice, and as far as possible, treatment with warfarin should be avoided because of the risks to the fetus. When patients are on long-term treatment with warfarin, pregnancy should be avoided, and warfarin should be discontinued prior to embarking on a pregnancy or as soon as pregnancy is suspected and before 6 weeks' gestation. In women from symptomatic families with antithrombin deficiency, adjusted dose heparin throughout pregnancy is recommended and warfarin for at least 3 months post partum. In protein C and protein S deficiency, factor V Leiden, or mutant factor II, treatment can be based on personal and family history. Thromboprophylaxis in late pregnancy and post partum should be considered. Fetal loss may be increased in women with inherited thrombophilia. The risk appears greatest in women with antithrombin deficiency and women with more than one thrombophilia defect. A number of reports have claimed that prophylactic treatment with heparin during pregnancy has resulted in successful pregnancy in women with recurrent fetal death and inherited thrombophilia.

Family Health↗
PubMed1999

Outcome of infected total knee utilizing a staging system for prosthetic joint infection.

This study reviews, over a 5-year period, the records of 70 consecutive patients with prosthetic knee infection and evaluates outcomes as a function of a staging system for prosthetic joint infection. The staging system for prosthetic joint infection was divided into three main categories that include infection type, systemic host grade, and local extremity grade. Outcome indices analyzed included Knee Society Score (KSS), complication rate, amputation rate, and rate of permanent resection. We show that categorizing and stratifying data for patients with infected total knee arthroplasty are useful. A universally accepted staging system would allow for more objective comparisons of treatments and may eventually define particular treatment regimens for particular classes of patients.

Aged↗
PubMed1998

The shrinking renal replacement therapy "break-even" point.

BACKGROUND: This study examines the current cost of live donor (LD) transplantation at our institution, and compares it with that of dialysis. METHODS: The study population consisted of 184 consecutive adult recipients of laparoscopically procured LD kidney transplants. Cost-containment measures instituted during this series included elimination of routine postoperative antilymphocyte induction and an accelerated discharge clinical pathway with planned discharge of the recipient on postoperative day (POD) 2. Costs of the transplants to Medicare were estimated from hospital charges, readmission rates, and immunosuppressant usage. These were compared with published costs of dialysis to Medicare in terms of a fiscal transplant-dialysis break-even point. RESULTS: Kaplan-Meier patient and graft survival rates at 1 year were 97 and 93%, respectively. Among patients followed for at least 90 days and treated with no induction and either cyclosporine-mycophenolate mofetil or tacrolimus-mycophenolate mofetil, acute rejection rates were low (27.6 and 13.9%, respectively). In the last 124 patients, 32.3% were discharged by POD 3 and 71.8% by POD 6, with corresponding mean transplant hospital charges (excluding organ acquisition) of $11,873 and $17,350, respectively. The 30-day readmission rate for patients discharged on the accelerated pathway by POD 3 was only 16%. The least expensive subgroup in the present study (30% of patients) was that of patients discharged by POD 6 and not readmitted during the first year; the break-even point with dialysis costs was calculated as 1.7 years after the transplant. CONCLUSIONS: The cost of LD transplants can be safely reduced by elimination of routine postoperative anti-lymphocyte immune induction and by an early discharge clinical pathway. Uncomplicated LD kidney transplants, meaning those with a short length of stay in the hospital after transplantation and no need for readmission within the first year, accrue savings over dialysis within 2 years.

Adolescent↗
PubMed1998

Hemostasis in the uteroplacental and peripheral circulations in normotensive and pre-eclamptic pregnancies.

OBJECTIVE: Our purpose was to determine the hemostatic changes in the uteroplacental and peripheral circulations in normotensive and pre-eclamptic pregnancies. STUDY DESIGN: This prospective, observational study involved 2 patient groups. Group 1 consisted of 30 normotensive women and 22 women with pre-eclampsia who were followed up longitudinally through pregnancy and post partum. Group 2 consisted of 20 women with established pre-eclampsia and 19 normotensive control subjects, all undergoing cesarean section. Plasma levels of thrombin-antithrombin III complex, soluble fibrin, plasmin-alpha2-antiplasmin complex, and fibrin-degradation product (D-dimer) were measured in blood drawn from the antecubital vein (group 1) and from both the antecubital and uterine veins (group 2). Data were analyzed by analysis of variance. RESULTS: In group 1 levels of thrombin-antithrombin III complex, soluble fibrin, and fibrin-degradation product were significantly higher during normal pregnancy than at 6 weeks post partum. Plasmin-alpha2-antiplasmin complex levels did not change. No differences between the pre-eclamptic and normotensive pregnancy groups were found for any of the hemostatic markers. In group 2 normotensive women undergoing cesarean section, thrombin-antithrombin III complex and soluble fibrin levels were significantly higher in the uterine vein than in the antecubital vein. In group 2 women with pre-eclampsia, thrombin-antithrombin III complex and fibrin-degradation product levels were significantly higher in the uterine vein than in the antecubital vein. In addition, plasmin-alpha2-antiplasmin complex and fibrin-degradation product levels were higher and soluble fibrin levels were lower in the uterine vein in the pre-eclamptic group than in the normotensive group. CONCLUSION: Both the coagulation and fibrinolytic systems are activated during normal pregnancy. Activation of these systems is more marked in the uteroplacental circulation than in the systemic circulation in both normotensive and pre-eclamptic pregnancies. An abnormal pattern of hemostasis occurs in the uteroplacental circulation in pre-eclampsia.

Adult↗
PubMed1998

Effects of oral contraceptives containing different progestogens on sodium-lithium countertransport in normal females.

In view of the lack of unanimity on the effect of long-term intake of combined oral contraceptives (OC) on external sodium-dependent lithium efflux, otherwise known as sodium-lithium countertransport (SLC), we undertook a double-blind study to investigate the possible interaction between SLC and OC in healthy women with regular menstrual cycles. In a group of 17 volunteers, aged 27.0 +/- 1.1 years (mean +/- s.e.m.) and weighing 61.4 +/- 2.0 kg, ingestion of 30 microg ethinyloestradiol + 150 microg desogestrel for 3 months caused an increase in SLC activity from a baseline value of 0.254 +/- 0.017 mmol/lcell x h to 0.274 +/- 0.017 mmol/lcell x h (P = 0.05). The activity of the transport system after 6 months treatment remained higher than at baseline (0.280 +/- 0.016 mmol/lcell x h, P < 0.025) but was comparable to that at 3 months. Blood pressure and weight remained unaltered during the study period. In a comparable group of 16 volunteers of age 26.1 +/- 1.3 years and weight 63.5 +/- 2.1 kg, control SLC activity (0.218 +/- 0.012 mmol/lcell x h) was comparable to that after 3 months (0.215 +/- 0.011 mmol/lcell x h) and 6 months (0.216 +/- 0.011 mmol/lcell x h) intake of 35 microg ethinyloestradiol + 2 mg cyproterone acetate. Body weight and blood pressure remained similarly unchanged. These results not only confirm that long-term intake of OC may cause increased SLC activity, but also suggest that the type of the progesterone in the medication used could be an important determinant of such interaction.

Adolescent↗
PubMed1998

Role of anticardiolipin antibodies in young persons with migraine and transient focal neurologic events: a prospective study.

Anticardiolipin antibodies (aCL) are a risk factor for cerebral ischemia. In migraine, the association is controversial, with widely varying results in different small series. The controversy in part may be due to the inherent difficulty in distinguishing the transient focal neurologic events (TFNE) of migraine from TIA. To assess the frequency of aCL in migraine, we prospectively evaluated consecutive adults under 60 years of age with migraine without aura and with recent TFNE (<24-hour duration) clinically suggestive of either migraine with aura or TIA. We concomitantly enrolled persons with no CNS disease. Each person was interviewed and had blood drawn for solid-phase ELISA with IgG and IgM aCL isotyping. Neuroradiologic studies were reviewed. Patients with TFNE were followed every 6 months for the duration of the 3-year study. The frequency of aCL positivity (IgG >20, IgG >40, IgM >7.5) for the 645 patients with TFNE (8.8, 3.1, 4.2%), the 518 persons in the TFNE subgroup with migraine with aura (8.9, 3.3, 4.1%), the 497 persons with migraine without aura (7.0, 2.0, 3.6%), and the 366 control subjects (9.3, 3.6, 3.9%) did not differ significantly between groups. In TFNE patients with elevated aCL titer, the association was positive with diabetes mellitus, TFNE duration <15 minutes, and diplopia and was negative with hemiparesis, tinnitus, and family history of stroke. Findings on imaging consistent with cerebral ischemia were more frequent in aCL-positive persons. The short-term risk of stroke was uniformly low. In young persons, aCL is not associated with migraine or with TFNE, although diabetes mellitus, negative family history of stroke, and brief duration of symptoms (including diplopia) may predict immunoreactivity. Imaging studies suggest an ischemic etiology of TFNE in this cohort.

Adolescent↗
PubMed1998

Inherited thrombophilia and pregnancy: the obstetric perspective.

The identified main causes of inherited thrombophilia are deficiencies of antithrombin (AT), protein C, or protein S, resistance to activated protein C associated with Factor V Leiden mutation, mutant factor II, and inherited hyperhomocysteinemia. For women from symptomatic families, these defects may be associated with an increased risk of venous thrombosis during pregnancy and/or recurrent fetal loss. Inherited thrombophilia is common and appears to be a multigenic disorder. The thrombotic risk seems to be greatest for women who have AT deficiency or more than one thrombophilic defect. The abnormalities that are now recognized are only part of the genetic predisposition to thrombosis. When assessing thrombotic risk during pregnancy, acquired risk factors as well as genetic predisposition should be considered. Increasing age, obesity, immobility, and delivery by cesarean section are major acquired risk factors. Pregnancy should be planned as far as possible, and each patient should be managed individually. During pregnancy, heparin is the anticoagulant of choice, and treatment with warfarin should be avoided because of risks for the fetus. When patients receive long-term treatment with warfarin, pregnancy should be avoided or planned, and warfarin should be discontinued before conception or as soon as pregnancy is confirmed and before 6-weeks' gestation. For women who have AT deficiency, the incidence of thrombosis during pregnancy is between 20 and 40%. Adjusted-dose heparin throughout pregnancy is recommended, followed by warfarin for at least 3 months postpartum. For patients who have Factor V Leiden, mutant factor II, or a deficiency of protein C or protein S, treatment can be based on personal and family history. Thromboprophylaxis during late pregnancy and postpartum should be considered. Fetal loss may be increased for women with inherited thrombophilia. The risk appears to be greatest for women with AT deficiency and women with more than one thrombophilic defect. For women with recurrent fetal death and inherited thrombophilia, a number of case reports claim that prophylaxis with heparin during pregnancy has resulted in successful pregnancy.

Anticoagulants↗
PubMed1997

Everyday problem solving across the adult life span: influence of domain specificity and cognitive appraisal.

Differences in problem-solving strategies for situations varying in three domains, consumer, home management, and conflict with friends, were examined among younger, middle-aged, and older adults. In addition, this study examined the influence of perceived ability to resolve the problem, controllability, and causal attributions on strategy selection. In the 2 instrumental domains, older adults were more problem focused in their approach than adolescents and younger adults, whereas adolescents and younger adults selected more passive-dependent strategies. In the more interpersonal domain, conflict with friends, older adults tended to select avoidant-denial strategies more so than younger adults. Finally, across domains, the greater the perceived ability to resolve a problem the less the avoidant-denial strategy was selected. The importance of distinguishing between social and instrumental problem solving and of examining the cognitive appraisal of a problem situation are discussed.

Activities of Daily Living↗
PubMed1995

Headache disability inventory (HDI): short-term test-retest reliability and spouse perceptions.

We have reported previously that the 25-item Headache Disability Inventory has good internal consistency reliability, robust long-term (2 month) test-retest stability, and good construct validity. We conducted further investigations to evaluate the short-term (1 week) test-retest reliability and spouse perceptions of patients' self-perceived headache disability. The short-term test-retest reliability of the Headache Disability Inventory was excellent. Additionally, the spouse and patients' perceptions of the patient's headache disability generally were congruent, although we observed instances where the differences were marked.

Adult↗
PubMed1992

The interaction of auramine O with calmodulin: location of the binding site on the connecting strand.

The cationic dye auramine O forms a fluorescent complex with Ca(2+)-liganded calmodulin. One moderately strong binding site is present, as well as one or more weaker sites. The binding site for auramine O is different from those for toluidinyl-naphthalene sulfonate. The dependence of binding upon electrolyte concentration suggests a substantial electrostatic component of the free energy of binding. The splitting of the bond between residues 77 and 78 by trypsin digestion abolishes auramine O binding; the N- and C-terminal half-molecules have virtually no binding capacity. This suggests that the primary binding site is located near the midpoint of the connecting strand and includes elements of both half-molecules. Thrombin digestion, which splits calmodulin between residues 106 and 107, also substantially reduces auramine O binding; this may be interpreted in terms of the stabilization of the structure of the connecting strand by interaction with residues within binding domain IV. The binding affinity at pH 5.0, where the helical organization of the connecting strand may be intact, is greater than at neutral pH.

Benzophenoneidum↗
PubMed1991

Prediction of the course of pre-type I diabetes.

To increase knowledge on the predictability of the onset of insulin-dependent diabetes mellitus (IDDM; type I), we followed 38 subjects less than 18 years of age who had positive results on two or more islet-cell antibody tests and one identical twin who had positive results on one islet-cell antibody test. All 39 patients had longitudinal intravenous glucose tolerance tests to determine the first-phase insulin response (FPIR). Insulin dependence has developed in 10 untreated subjects less than 18 years of age. Of the 10 subjects, insulin dependence developed in eight a mean of 4.6 months after their FPIR fell to less than 30 microU/ml and a mean of 14 months after it fell to less than 46 microU/ml. Nine of the untreated subjects had an FPIR less than 67 microU/ml on at least two occasions and became insulin dependent a mean of 19 months after the value first fell below this level (95% confidence limit = 66.4% to 100%). All but one of the 10 subjects in whom IDDM developed initially had islet-cell antibody levels of greater than 80 JDF units. Insulin autoantibody values at onset were available for 9 of the 10 subjects and were positive (greater than 39 nU/ml) in six. We conclude that the combination of positive results on two islet-cell antibody tests and two diminished FPIRs (less than 67 microU/ml) in subjects less than 18 years of age reliably predicts the onset of IDDM. These data should permit intervention studies to be planned.

Adolescent↗
PubMed1987

The interaction of melittin with troponin C.

Melittin has been found to interact with troponin C with high affinity in the presence of Ca2+. The association constant approaches in magnitude that for melittin and calmodulin. The interaction results in a shift to lower wavelengths of the emission band of Trp-19 of melittin and in an increased shielding of Trp-19 from quenching. A major increase occurs in the alpha-helical content of combined melittin. Formation of the complex inhibits tryptic hydrolysis of the connecting strand. The properties of fluorescent labels attached to Met-25 and to AEDANS-98 are altered as a result of the interaction. It is concluded that the combined melittin makes extensive contact with the connecting strand and adjacent portions of the N- and C-terminal lobes.

Animals↗
PubMed1987

Rotational modes of Ca2+-liganded calmodulin, as determined by time-domain fluorescence.

The time decay of fluorescence anisotropy was monitored as a function of pH and temperature for complexes of 2,6-toluidinylnaphthalenesulfonate with calmodulin, with its proteolytic fragments, and with the 1:1 complex of calmodulin and melittin. For all the conditions examined the anisotropy decay of native calmodulin involved at least two rotational modes. These corresponded to a short correlation time of 2-3 ns, reflecting a localized motion in the vicinity of the binding site and a longer correlation time which arises from the rotation of a major portion of the molecule. The relative amplitudes of the two rotational modes were dependent upon temperature in the range 11-40 degrees C, the contribution of the more rapid mode increasing with temperature. The maximum immobilization of the probe occurred at pH 5.0 and 12 degrees C. While these results indicate the presence of internal rotations in Ca2+-liganded calmodulin, the magnitude of the longer correlation time is consistent with the crystallographic structure.

Animals↗