PubMed Health⌕ Search

Biomedical subjects

R H Christenson

Publications and source records attributed to R H Christenson.

83 records · Page 5Linked to original sources
PubMed1985

Results of dipstick tests, visual inspection, microscopic examination of urine sediment, and microbiological cultures of urine compared for simplifying urinalysis.

Using microscopic sediment examination, reagent dipsticks, visual appearance, and microbiological culture, we studied 196 urine specimens collected under sterile conditions. We conclude that the sensitivities and specificities noted in the comparison of dipstick urinalysis with urine microscopy justify eliminating many microscopic examinations if a procedural flowchart is used. All 33 (16.8%) of the uncontaminated urine specimens showing substantial potential pathogen content on culture had either a turbid appearance or positive results for one or more dipstick tests. A positive dipstick test result for nitrite most consistently indicated that the urine should be cultured.

Bacteriuria↗
PubMed1985

Two radioassays for serum vitamin B12 and folate determination compared in a reference interval study.

For 154 subjects, we verified that vitamin B12 and folate status was normal, using as criteria the average polymorphonuclear lobe count, mean corpuscular volume, and hemoglobin concentration. We then used blood from these subjects to compare values obtained with two radioassay kits, each designed for simultaneous vitamin B12 and folate determination. Although regression analysis showed reasonable correlation between the folate (r = 0.87) and vitamin B12 (r = 0.94) kits, we observed significant differences in the overall mean values for vitamin B12 (p less than 0.01) and folate (p less than 0.001) as measured with the kits in this population. Radioassay standard-curve data for the folate assays were similar, but these data indicated greater sensitivity at low concentrations for one vitamin B12 kit than the other. Using reference intervals recommended in the kit inserts, we found that the vitamin B12 status for 9% of these subjects would have been misclassified by one kit, 2% by the other.

Anemia, Megaloblastic↗
PubMed1984

Bioavailability of digoxin capsules and tablets: effect of coadministered fluid volume.

The effect of different coadministered fluid (water) volumes on the consistency of digoxin absorption was studied in 16 male volunteers. Each volunteer received four single-dose treatments (two 0.25-mg digoxin tablets with 30- and 240-mL of water and two 0.2-mg digoxin capsules with 30- and 240-mL of water). Digoxin present in serum and urine samples collected for 48 h after dosing was quantified by RIA. Treatments were compared by evaluating the following model-independent pharmacokinetic parameters: maximum serum concentration (Cmax); time of maximum serum concentration (tmax); area under the serum concentration-time curve for 0-12 h (AUC0-12); cumulative urinary excretion for 0-48 h (CUE48). No significant differences were found between dosage form (tablets versus capsules) and coadministered water volume (30 mL versus 240 mL) for any of the parameters. For both fluid volumes the AUC0-12 and Cmax were significantly larger (p less than 0.01) and the tmax significantly shorter (p less than 0.01) for the capsules than for the tablets. The volume of coadministered water had no effect on the amount of digoxin absorbed from either dosage form.

Adult↗
PubMed1983

Interpretation of cerebrospinal fluid protein assays in various neurologic diseases.

Albumin and immunoglobulin G (IgG) were determined in cerebrospinal fluid (CSF) and serum, and the CSF/serum albumin Index (CSF X 10(3)/serum albumin concentration ratio) and IgG Index [(CSF/serum IgG)/(CSF/serum albumin)] were calculated. Data for these indices and oligoclonal banding are described in 23 cases of multiple sclerosis (MS), 19 of systemic lupus erythematosus (SLE), eight of sarcoidosis, 48 cases of miscellaneous disease, and 25 control patients with nonspecific complaints. Of the MS, SLE, and sarcoidosis patient groups, 8.5%, 26%, and 12.5% showed an abnormally high CSF/serum albumin Index; 87%, 16%, and 0% an increased IgG Index; and 87.5%, 42% and 0% showed positive oligoclonal banding. IgG Index and oligoclonal banding results for MS patients differed significantly from the sarcoidosis (p less than .001) and SLE (p less than .05) groups. When the CSF/serum albumin Index is considered also, the control and sarcoidosis patient results differ significantly from the MS group (p less than .001 and p less than .01). A strong correlation between the IgG Index and oligoclonal banding is implicated.

Blood-Brain Barrier↗
PubMed1982

A routine method for the determination of digoxin in urine by radioimmunoassay.

We describe a radioimmunoassay for the routine determination of digoxin in urine employing readily available commercial reagents. The standard curve was found to exhibit very good linearity represented by a composite correlation coefficient of 0.9993 and a standard error of estimate which was less than 1% of the digoxin concentration range of interest. Between-assay precision was excellent as reflected by the coefficient of variation (CV) which averaged 5.29%. Studies assessing the recovery of the present method showed satisfactory results of 106% at a low level of digoxin excretion and 102% at a higher excretion level. Our laboratory carried out a study of digoxin bioavailability in which a standard digoxin dose of 500 micrograms was given to 16 volunteers and the present radioimmunoassay method was employed to measure digoxin excretion. An amount equal to 33.4 +/- 6% of the drug given was eliminated 48 h following digoxin dosing.

Biological Availability↗
PubMed1982

Simplified fluorometry of total metanephrines in urine.

We describe a simplified fluorometric method for quantitatively determining metanephrines in urine. The method is based on the elution of metanephrines from an ion-exchange column followed by production of a fluorescent derivative that has excitation and emission maxima of 405 nm and 505 nm, respectively. Metanephrine concentrations as great as 7.0 mg/L were within the linear range of the assay. Analytical recovery of metanephrines was 82-87%. Cross contamination by catecholamines was insignificant. The upper range of normal was 520 micrograms/24 h. Within-run and between-run CV's were 5% and about 9%, respectively. Twenty-four-hour urine specimens from five patients with pheochromocytoma showed above-normal amounts of the metanephrines by this method.

Adrenal Gland Neoplasms↗
PubMedDate not supplied

Creatine kinase and its CK-MB isoenzyme: the conventional marker for the diagnosis of acute myocardial infarction.

Biochemical markers are commonly used for detection, diagnosis, and management of various diseases. Creatine kinase (CK) is an enzyme found in most tissues, and is the best known marker for the identification of acute myocardial infarction (AMI). We review the most common techniques used to quantify creatine kinase and its cardiac specific fraction, CK-MB. Electrophoresis, immunoinhibition, monoclonal immunoassay, and CK-MB isoform assays are considered for efficacy, sensitivity and specificity, and timeliness in the setting of acute non-traumatic chest pain. Limitations of the various techniques for identifying AMI are identified. Current recommendations for CK-MB panels, including combinations with other cardiac markers, are included.

Algorithms↗
PubMedDate not supplied

Determinants of elevated blood lead levels among working men in Greater Beirut.

This cross-sectional study reports the blood lead levels (BLL) among different working groups in Beirut and identifies the risk factors associated with elevated BLLs. A total of 579 men of 18 years of age or older (response rate 96%) working in Greater Beirut were interviewed. Of those, 315 (54.4%) provided a blood sample of which 291 were analyzed for lead. The mean BLL of the 134 men working in white-collar jobs (offices, retail shops) was 12.7 microg/dl (SD 3.7); statistically significantly lower than the mean BLL (18.4 microg/dl; SD 9.8) of the 157 men working in blue-collar occupations (such as gas station attendants, painters, mechanics). A blood lead level of 15 microg/dl or more was associated with blue-collar jobs, number of cigarettes smoked, commuting > or = 3 km to work, years in current occupation, and younger age. A BLL of at least 20 microg/dl was associated with eating lunch at work, in addition to blue-collar jobs, smoking, commuting, years of work, and younger age. The study findings suggest that environmental exposure (those not otherwise exposed to occupational lead) is mainly determined by smoking and exposure to leaded gasoline (commuting). Occupational exposure to lead is prevalent among a wide spectrum of Lebanese workers. Physicians are called upon to inquire more about the potential for lead exposure, especially among blue-collar workers. A policy action to improve working conditions and to phase out the use of leaded gasoline is recommended.

Adolescent↗
PubMedDate not supplied

Cerebrospinal fluid and plasma apolipoproteins in patients with multiple sclerosis.

Apolipoprotein (apo) E is synthesized by cells of the central and peripheral nervous systems, and its synthesis and secretion in the peripheral nervous systems, and its synthesis and secretion in the peripheral nervous system of animals are greatly stimulated following Wallerian degeneration. It has been suggested that apo E functions in the metabolism of myelin lipids, but its physiologic role in nervous tissue has not been elucidated. To determine if apo E might play a role in demyelinating neuropathy, the concentrations were examined of apos E and A-1 in the cerebrospinal fluid (CSF) and plasma of patients with multiple sclerosis during clinical remission, and in patients with no neurologic disease. Serum and CSF albumin concentrations were measured to account for the possible influences of serum apo E concentration and/or altered blood-brain barrier permeability on the CSF apo E pool. A CSF index for apo E and apo A-1 was calculated in the same manner presently used for calculation of immunoglobulin G (IgG) production in the nervous system of patients with multiple sclerosis (MS). The results showed that the concentrations of apo E, apo Al, and albumin in the CSF of the MS patients were not significantly altered. The concentration of apo E in the serum, however, was significantly (p less than 0.001) decreased by 44 percent in the MS patients. The difference was relatively specific for serum apo E because the serum apo Al and albumin concentrations were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗