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Biomedical subjects

L Nelson

Publications and source records attributed to L Nelson.

At least 109 records · Page 6Linked to original sources
PubMed1991

Differential diagnosis of acute viral hepatitis using rapid, fully automated immunoassays.

We report the development of three rapid, fully automated immunoassays allowing the differential diagnosis of acute viral hepatitis. These assays detect HBsAg, IgM antibody to hepatitis B core antigen (IgM anti-HBc) and IgM antibody to hepatitis A virus (IgM anti-HAV) using the IMx instrument system. All IMx assays were run in less than 45 minutes and all steps were fully automated including specimen dilution steps. Specimens from blood donors, diagnostic and hospital patients, and individuals with a variety of infectious and immune diseases were tested for IgM anti-HAV (n = 1473) or for IgM anti-HBc (n = 1606) or for HBsAg (n = 9700) by the IMx and commercially available EIA and RIA. Each IMx assay showed 99.8% agreement with current EIA. Reproducibility in all hepatitis IMx assays was significantly better than that observed with manual or semiautomated assays; within-run and between-run % CV ranged from 2.2 to 4.8 and 3.5 to 10.3 respectively. In 29 acute hepatitis B patients studied, HBsAg and IgM anti-HBc were detected in the first available patient bleed collected from 0 to 4 week from the onset of symptoms. IgM anti-HBc persisted at reactive levels in the IMx assay for 1 to 24 weeks (mean 12.1 +/- 5.3 weeks) after the patient presented with symptoms. In individuals exposed to hepatitis A, IgM anti-HAV was detectable by IMx by 40 days post exposure (average 33.5 days) and IgM had declined to unreactive levels in IMx for all patients by from 3 to 6 months post exposure. These data demonstrate the use of these rapid IMx assays for differentiation of acute hepatitis A and B.

Acute Disease↗
PubMed1991

Quantitation of hepatitis B surface antibody by an automated microparticle enzyme immunoassay.

A fully automated microparticle enzyme immunoassay, IMx AUSAB, was developed for the detection and quantitation of antibody against hepatitis B surface antigen (anti-HBs). The IMx AUSAB assay can complete 24 tests in less than 45 minutes. Anti-HBs concentrations in specimens are calculated automatically by comparison of the specimen rate to values determined from a stored standard curve. IMx AUSAB sensitivity is 2-3 mIU/ml, equivalent in sensitivity to AUSAB RIA or EIA. Specimens from blood donors, diagnostic and hospital patients, hepatitis B vaccinees, and individuals with a variety of infectious and autoimmune diseases tested in parallel by IMx AUSAB and AUSAB RIA or IMx AUSAB and EIA gave overall qualitative agreement of 97.8% (1265/1293) and 99.1% (1281/1293), respectively. The prevalence of anti-HBs ranged from 5.9% in volunteer blood donors to 47.0% of specimens from a sexually transmitted disease clinic. Most discordant specimens (18/34) were low level reactive (less than 10 mIU/ml) by AUSAB RIA, but negative by IMx AUSAB and AUSAB EIA. These specimens were also negative for antibodies to hepatitis B core antigen (anti-HBc). Six discordants were low level reactive by IMx but negative by RIA and EIA. Three of these six specimens were also reactive for anti-HBc suggesting that the IMx AUSAB reactivity resulted from the presence of low level anti-HBs. Quantitative agreement between IMx AUSAB and RIA or IMx and EIA for 106 specimens ranging in anti-HBs concentration from 1 to 30,000 mIU/ml gave linear correlation coefficients of 0.91 and 0.96, respectively. The IMx test was useful for monitoring hepatitis B vaccine response and seroconversion levels after hepatitis B infection.

Automation↗
PubMed1991

What is the dose-response relationship between exercise training and blood pressure?

Most studies of exercise and blood pressure have used a standard exercise programme with a single level of physical activity. To determine the nature of the dose-response relationship however it is necessary to examine several levels of activity, preferably in the same subjects. We have recently performed several randomised crossover studies comparing different levels of regular exercise. The intensity and duration of exercise bouts were constant throughout the studies, but their frequency was varied. Standard bouts consisted of 30 min of bicycling at 60%-70% of maximum work capacity. The exercise was performed either three-weekly or 7-weekly in randomised order and each level was maintained for one month. In sedentary normal subjects three bouts of exercise/week for a total of 90 min lowered blood pressure by 10/7 mmHg. With seven bouts, i.e. a total of 210 min exercise/week, blood pressure was only slightly lower than 3-week exercise and was 12/7 mmHg below sedentary values. Responses to measures of physical fitness including maximum oxygen consumption and work capacity were linearly related to the amount of exercise performed each week. Similar results were obtained in hypertensives. Another randomised study was performed amongst expeditioners to Antarctica where environmental conditions determined that they were sedentary in winter and active in summer. The addition of either 3-week or 7-week exercise in winter significantly lowered blood pressure. In summer when the background level of activity was higher, blood pressure with no added exercise was similar to exercising levels in winter. There was no further fall in blood pressure with either 3-week or 7-week additional exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Intramammary challenge with Escherichia coli following immunization with a curli-producing Escherichia coli.

Holstein and Jersey cattle were immunized with a curli-producing strain of Escherichia coli (pCRL65/A012) or a noncurli-producing strain (pUC18/HB101) to determine differences in resistance to establishment of experimental intramammary infection. Cows (n = 6 per group) were immunized at 14 d prior to drying off, 7 d of involution, and at calving with 3 x 10(10) E. coli in Freund's Incomplete Adjuvant. At 30 d of lactation, one mammary quarter of each cow was infused with a wild strain of E. coli (727). Escherichia coli 727 was isolated from a naturally occurring intramammary infection and produced curli. All challenged quarters became infected, and all cows developed acute clinical mastitis. Geometric mean duration of intramammary infections was 6 d for both immunization groups. All infections were spontaneously eliminated within 10 d. No differences occurred between immunization groups in blood selenium and glutathione peroxidase activity, plasma selenium, number of E. coli 727 isolated from secretion after challenge, rectal temperature and SCC response, clinical status of mammary quarters, or DMI. Reduction in milk production after challenge was greater for cows immunized with E. coli pCRL65/A012. Immunization of dairy cattle with a curli-producing strain of E. coli did not protect against experimental intramammary challenge during lactation.

Animals↗
PubMed1991

Medigap preferred provider organizations: issues, implications, and early experience.

The Health Care Financing Administration is sponsoring the Medicare Physician Preferred Provider Organization (PPO) Demonstration to assess the feasibility and desirability of including a PPO option under Medicare. Two sites are currently operational. At one site, Blue Cross and Blue Shield of Arizona is offering a PPO linked with a medigap insurance plan. This "medigap PPO" and its initial experience are described, and a preliminary assessment of the viability and effectiveness of medigap PPOs nationally is provided. Impediments to the development and effectiveness of medigap PPOs are identified and possible government actions discussed.

Aged↗
PubMed1991

The automated modified Russell viper venom time test for the lupus anticoagulant.

Antiphospholipid antibodies, both anticardiolipin antibody and lupus anticoagulant, are associated with a hypercoagulable state, manifested as thrombotic events and pregnancy losses. Multiple coagulation tests are available for the lupus anticoagulant, but few are in wide use. The modified Russell viper venom test (RVVT) is one of several excellent tests for the lupus anticoagulant, with high sensitivity and specificity. We present an automated method for measuring the RVVT and demonstrate its reproducibility.

Automation↗
PubMed1991

The role of calcium channel blockers in the treatment of essential hypertension.

Calcium channel blockers, originally developed for the treatment of angina and supraventricular arrhythmias, have been shown to lower elevated blood pressure effectively in hypertensive patients. Verapamil, nifedipine, and diltiazem represent prototype compounds for unique chemical classes with differing pharmacologic properties. These drugs lower elevated blood pressure with efficacy comparable with other commonly used antihypertensives. Combination therapy with other agents usually results in an additive response. Side effects are usually mild and reversible and usually are an extension of the drug's pharmacologic effects. Moreover, adverse metabolic effects on lipid, glucose, or potassium levels are not common. Because of the excellent antihypertensive effects of calcium channel blockers and their potential importance in a variety of other disease states, these agents should be routinely considered for use as a first-line antihypertensive agent in appropriately selected patients with hypertension of any severity as part of a comprehensive plan to minimize cardiovascular risk.

Animals↗
PubMed1990

Quantitation of skeletal muscle necrosis using 99Tcm-pyrophosphate with SPECT in a canine model.

Patients with acute arterial occlusion may suffer from significant muscle necrosis. It is important to determine the amount of regional muscle necrosis for prognostic purposes and evaluation of therapy. We have used technetium-99m-pyrophosphate (PPi) with single photon emission computed tomography (SPECT) to quantitate muscle necrosis. A canine gracilis muscle ischaemia model was used. PPi was injected 1.5 h before the muscle preparation was removed from the dog. SPECT was performed on the muscle preparations. An automatic edge detection program using the threshold technique determined the number of pixels with significant PPi activity in each transaxial section. Volume was calculated by summing the number of pixels with significant PPi activity and multiplying by the voxel size. The results were compared with quantitation using computerized planimetry with nitroblue tetrazolium staining (correlation coefficient = 0.93). PPi with SPECT is an accurate method for quantiating muscle necrosis.

Animals↗
PubMed1990

Neonatal cocaine-related seizures.

Cocaine abuse is associated with a variety of severe acute neurologic complications typically occurring in the abusers themselves. These include ischemic stroke, subarachnoid and intraparenchymal hemorrhage, headaches, syncope, seizures, and death. Sixteen pediatric patients with presumed cocaine-related seizures secondary to maternal consumption are reported. They were evaluated only because of requests for neurologic consultation. All were seen during the 1987 calendar year at the King/Drew Medical Center and Urban Comprehensive Epilepsy Program of Los Angeles. The cohort had similar maternal pregnancy histories and uniformly presented with postdelivery tremulousness, irritability, and excessive startle responses. Shortly after birth, each patient began having stereotypic episodes with ictal electroencephalographic confirmation in seven. Eight of these neonates continued to have seizures after the initial month of life.

Cocaine↗
PubMed1990

Effect of local stimulation of one quarter on milk production and milk components.

The existence of local udder regulatory mechanisms involved in the regulation of milk production was demonstrated. Because the four quarters of the udder are independent, yet share a common environment, the experiment was designed to give one quarter extra stimulation by hand-milking while the other quarters were machine-milked. A difference in milk production was found, proving the existence of local mechanisms. The largest differences were during evening milking with an increased production in the hand-milked quarter. The machine-milked quarters did not increase their production. The increased production was probably due to enhanced activity in the secretory cells, induced by some factor produced or activated locally in the udder.

Animals↗
PubMed1990

Cocaine-related seizures in adults.

Cocaine abuse is associated with a variety of severe acute neurologic complications. These include ischemic stroke, subarachnoid and intraparenchymal hemorrhage, syncope, seizures, and death. Eleven adult patients with cocaine-related seizures are reported. All were seen during the 1987 calendar year at the King/Drew Medical Center and Urban Comprehensive Epilepsy Program of Los Angeles. Three apparent clinical circumstances with defined methods of intake and time course after usage were identified in our cases. Seizures occurred 1) as acute provoked convulsions in patients known to have epilepsy, 2) spontaneously in otherwise normal individuals after acute snorting or "crack smoking," and 3) agonally with massive ingestion.

Adult↗
PubMed1990

An all-polyethylene cementless tibial component. A five- to nine-year follow-up study.

An all-polyethylene cementless tibial component was used in 221 total knee arthroplasties. With one exception, failures did not occur before three years. Failure was characterized by medial subsidence of the tibial component. There was abrasion of the polyethylene on the undersurface of all components that failed. Survivorship was seven to nine years (87.1%). This study demonstrated that a flexible cementless component can function well when used with any type of bone. However, abrasion of the polyethylene that occurs from shearing forces is a concern. Polyethylene components need adequate provisions to prevent shearing or need surface treatment to prevent abrasion.

Adult↗
PubMed1989

Complex partial status epilepticus provoked by "crack" cocaine.

A 53-year-old woman with a history of chronic abuse of "crack" cocaine developed isolated complex partial status epilepticus after 3 days of frequent cocaine use. The electroencephalogram demonstrated focal epileptiform activity. Follow-up for 1 year during which she reported continuous abstinence from cocaine and anti-convulsants revealed no recurrence of seizures.

Cocaine↗