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Biomedical subjects

J R Pearson

Publications and source records attributed to J R Pearson.

At least 19 recordsLinked to original sources
PubMed1995

Investigation of the impurities found in methamphetamine synthesised from pseudoephedrine by reduction with hydriodic acid and red phosphorus.

The synthesis of methamphetamine from pseudoephedrine via the reduction with hydriodic acid and red phosphorus was studied and the impurities which were generated, along with the methamphetamine, were investigated. Some of the impurities found have been reported previously, while the diastereoisomers of N-methyl-N-(alpha- methylphenethyl)amino-1-phenyl-2-propanone and the cis-cinnamoyl derivative of methamphetamine are reported here for the first time. Further work on the sequence of reactions occurring in this reduction is also reported.

Acids↗
PubMed1994

Hypertriglyceridemic serum, very low density lipoprotein, and iron enhance Mycobacterium avium replication in human macrophages.

The growth of Mycobacterium avium 7497, serovar 4, in cultured human macrophages is enhanced by Fe3+ and serum lipids over 7 days. Iron (1-80 micrograms/mL) added to macrophages cultured in normal serum resulted in 10-fold increases in growth. If iron-supplemented macrophages were cultured in serum from hypertriglyceridemic donors after infection, M. avium growth increased 10(3)- to 10(4)-fold. Without macrophages, differences in bacterial growth between sera were not seen. Removal of very low density lipoprotein (VLDL) eliminated the differences between sera. Isolated VLDL from hyperlipidemic serum resulted in 10(5)-fold increases in growth over that seen with VLDL from normal sera. Accelerated M. avium growth in macrophages cultured with hyperlipidemic serum was partly inhibited by the addition of superoxide dismutase (1000 IU/mL). Results suggest that iron stimulates O2-induced oxidation of VLDL and its subsequent accumulation in macrophages. The resultant iron- and lipid-laden cells become excellent hosts for mycobacterial growth.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Lithium absorption prevented by sodium polystyrene sulfonate in volunteers.

STUDY OBJECTIVE: To determine if sodium polystyrene sulfonate prevents absorption of lithium in human beings. DESIGN: Prospective, crossover study. TYPE OF PARTICIPANTS: Healthy volunteers age 22 to 34 years (three women and three men). INTERVENTIONS: After an eight-hour fast, subjects ingested 0.5 mEq/kg (18.5 mg/kg) lithium carbonate. One hour later, they ingested either 857 mg/kg sodium polystyrene sulfonate in 4 mL water/g sodium polystyrene sulfonate (experimental) or an equal volume of water without sodium polystyrene sulfonate (control). MEASUREMENTS AND MAIN RESULTS: Serum lithium levels were drawn zero, one, two, three, four, six, eight, ten, 12, and 24 hours after lithium ingestion. The sodium polystyrene sulfonate group had a smaller mean area under the serum concentration curve (11.6 +/- 1.0 mEq/L.hr versus 13.6 +/- 1.5 mEq/L.hr, P < .001) and lower mean highest measured lithium level (0.85 +/- 0.11 mEq/L versus 1.05 +/- 0.10 mEq/L, P < .05) compared with the control group. There was no significant difference in 24-hour urine lithium excretion or in serum sodium and potassium levels. CONCLUSION: Sodium polystyrene sulfonate administration decreased absorption of lithium after a lithium carbonate overdose. Sodium polystyrene sulfonate may be useful clinically for gastric decontamination after lithium overdoses.

Absorption↗
PubMed1991

The rise in the total iron-binding capacity after iron overdose.

STUDY OBJECTIVES: To determine if and to what extent the total iron-binding capacity (TIBC) would increase following an iron overload, and to identify specific iron-binding proteins that might be responsible for the increased TIBC. DESIGN: A prospective laboratory investigation. SETTING: A certified regional poison control center. PARTICIPANTS: Six healthy adult male volunteers. MEASUREMENTS AND MAIN RESULTS: All volunteers ingested 20 mg/kg of elemental iron. Blood samples were drawn at hourly intervals for eight hours and analyzed for serum iron, TIBC, transferrin, ferritin, lactoferrin, glucose, bicarbonate, and WBC. Within two hours of ingestion, subjects developed symptoms of toxicity, including nausea, lightheadedness, vomiting, severe crampy abdominal pain, and voluminous diarrhea. The TIBC was statistically significantly increased at all points measured from one to six hours. Despite rising above 300 micrograms/dL in five of six subjects, the serum iron never exceeded the TIBC in any subject. Transferrin and ferritin did not increase to account for the increased TIBC. The lactoferrin levels did increase, but they did not correlate with significant increases in the TIBC. CONCLUSIONS: Twenty mg/kg of elemental iron caused clinical toxicity in this study, and after iron overload the colorimetric TIBC increased by unknown mechanisms.

Adult↗
PubMed1990

First-order model for the analysis of stump stresses for below-knee amputees.

This study extends what had been a purely numerical model that used influence-factor matrices to relate the stump stresses to prosthesis loads for unilateral, below/knee amputees. Previously published influence-factor matrices are now factored into a coefficient matrix times the inverse of a stump geometry matrix. Using actual stump parameters, new information is learned about how the resistive moment of the stump balances the flexion-extension moment of the prosthesis and why certain normal stresses reach a maximum during a specific portion of the stance phase of the prosthesis.

Amputation Stumps↗
PubMed1990

Evaluation of the clinical usefulness of a chemiluminometric method for measuring creatine kinase MB.

The use of creatine kinase isoenzymes (CK-MB) in the diagnosis of acute myocardial infarction (AMI) is well established. We evaluated the use of a new chemiluminometric method (CK-Ciba) for measuring CK-MB by calculating its sensitivity, specificity, positive and negative predictive values, and diagnostic efficiency for diagnosing AMI. We tested 633 samples from 229 patients within 4 h of receipt. The patients were divided into four groups: (1) patients who had an AMI, (2) patients who had AMI ruled out, (3) patients who had CK-MB measured for reasons other than to rule out AMI, and (4) patients who had only one sample drawn. Only patients in Groups 1 and 2 were used in the study. AMI was diagnosed by a cardiologist. The prevalence of AMI in our population was 0.18. A receiver-operator characteristic curve was used to establish optimal values for identifying AMI with the CK-Ciba results: CK-MB greater than or equal to 10 micrograms/L and a CK-MB index of greater than or equal to 3.0 (micrograms of CK-MB per U of CK x 100). Using these values, we calculated a sensitivity of 1.00, specificity of 0.97, positive predictive value of 0.87, negative predictive value of 1.00, and a diagnostic efficiency of 0.97. We conclude that the CK-Ciba method has high sensitivity, high specificity, and good predictive values for CK-MB and is appropriate to use to rule out AMI.

Creatine Kinase↗
PubMed1990

The fall of the serum anion gap.

Using modern electrode technology (Beckman ASTRA analyzer), we evaluated the reference range for the anion gap (calculated as sodium minus chloride minus bicarbonate concentrations) in serum to determine whether the 8 to 16 mmol/L reference range in common use is still valid. After measurement of electrolytes in (1) serum from 29 healthy volunteers, (2) aqueous standards verified against National Bureau of Standards reference material, and (3) serum from 120 blood donors, we drew the following conclusions. (1) The reference range for the anion gap has shifted downward (to 3 to 11 mmol/L in one of our laboratories), primarily because of an upward shift in chloride values. (2) Using the ASTRA analyzer, a majority of normal individuals can be expected to have serum anion gaps of 6 mmol/L or less unless chloride calibration is deliberately altered. (3) If the anion gap is to remain an effective tool in diagnosing acid-base disorders, clinicians need to be aware that the traditional reference range may not be appropriate with new instrumentation.

Acid-Base Equilibrium↗
PubMed1988

Evaluation of a simple method for measuring blood cholesterol levels using non-laboratory observers.

PURPOSE: Blood cholesterol is a good estimator of risk for coronary heart disease. Six criteria for a screening cholesterol measurement are: (1) high predictive value of elevated cholesterol compared with a "gold standard" cholesterol measurement; (2) high correlation with the national reference system for cholesterol; (3) acceptable results obtainable by volunteer observers; (4) results available quickly; (5) reproducible results; and (6) low cost. We hypothesized that cholesterol measurements performed on the Reflotron by volunteer nurses would meet these criteria. SUBJECTS AND METHODS: We recruited 345 subjects (160 men, 185 women, aged 20 to 84) and measured their blood cholesterol level by a method calibrated under the National Heart, Lung, and Blood Institute Lipid Standardization Program (Lab-chol) and on the Reflotron (R-chol method). RESULTS: Comparison of the results showed good agreement (slope = 0.937; intercept = 0.27 mmol/liter). Comparison of the risk assignments made by the R-chol method against those made by the Lab-chol method, using the 1987 Adult Treatment Panel classification criteria, showed that the R-chol method has a sensitivity of 0.79 and a specificity of 0.98. Assuming a national prevalence of hypercholesterolemia of 25 percent, the positive predictive value is 0.92 and the negative predictive value is 0.93. The cost per screen was $1.25. CONCLUSION: These data show that volunteer observers can obtain screening cholesterol results on the Reflotron that are accurate, reliable, quickly available at a low cost, and have high predictive value for hypercholesterolemia.

Adult↗
PubMed1988

The effect of selective D1 and D2 dopaminergic agents on sexual receptivity in the female rat.

A number of dopaminergic drugs was tested for their effect on female sexual receptivity in ovariectomised plus adrenalectomised rats primed with oestradiol benzoate. The selective D1 agonist (SKF 38393 5-40 mg/kg) and D1 antagonist (SCH 23390 0.1-10 mg/kg) had no significant effect on sexual behaviour. The results of administration of mixed dopaminergic agents (DOPA, 10-50 mg/kg with benserazide or 100-200 mg/kg alone and haloperidol 0.01-1.0 mg/kg) and selective D2 dopaminergic agents (LY 171555 2.5-800 micrograms/kg, BHT 920 0.01-1.0 mg/kg and sulpiride 5-80 mg/kg) indicate that a central dopaminergic system has an inhibitory control on female sexual activity exerted through D2 receptors. Any stimulatory effects of the exogenous agonists were probably due to an action on presynaptic D2 receptors. The predominance of the D2 pre- and post-synaptic receptor activity appears to be influenced by the sexual receptivity of the animal.

Animals↗
PubMed1988

Analytical description of minimum energy expenditure surfaces.

Mechanical energy expenditure during level walking was evaluated and graphed for two unilateral, below-knee amputees over time and a range of adjustments of the flexion-extension alignment angle. The resulting mechanical energy surfaces were then least-squared fitted with an analytical function that was linear in time and quadratic in flexion-extension alignment angle. The least-squares analysis showed that there was a flexion-extension adjustment that minimized the mechanical energy expenditure and that this optimal adjustment was very close to the design point set by certified prosthetists.

Artificial Limbs↗
PubMed1987

Least-squares matrix correlations between stump stresses and prosthesis loads for below-knee amputees.

Stump stresses were correlated to prosthesis loads for two unilateral, below-knee amputees over a range of flexion-extension angular adjustments. Normal stresses on the patellar tendon and gastrocnemius were related to the axial force and flexion-extension moment of the prosthesis via a matrix equation. Elements of this matrix, influence factors calculated by least-squares algorithms, identified the contributions of each time-dependent load component acting to produce the time-dependent normal stresses. The flexion-extension angular sensitivity of the way these sagittal plane loads combined to produce normal stresses was included in the matrix equation via a first-order Maclaurin series. Highly favorable correlation coefficients between empirically measured and theoretically predicted stump stresses were calculated. This demonstrated that, in future studies, using an influence-factor matrix holds promise for quantifying sensitivities of normal stresses of the stump to multiple adjustments in prostheses.

Amputation Stumps↗
PubMed1986

The effect of neonatal manipulation of hypothalamic serotonin levels on sexual activity in the adult rat.

5HT and 5HIAA levels were altered in neonatal males and females by treating them with 100 mg/kg p-chlorophenylalanine (PCPA) or 20 mg/kg 5-hydroxytryptophan (5HTP) over eight days 1 to 7 or 11 to 16 of life. Androgenized females (testosterone propionate given on day 1) were also treated over days 1 to 7. In adulthood the effects of these treatments on sexual behaviour were observed. None of the treatments affected feminine sexual behaviour in either sex. Reduction of 5HT activity by PCPA enhanced masculine sexual behaviour in males and potentiated the defeminizing effect of exogenous testosterone in females. Increasing 5HT by 5HTP antagonised the defeminizing effect of exogenous testosterone. These findings indicate that the lower levels of hypothalamic 5HT and 5HIAA seen in the neonatal males may have some physiological importance, since 5HT appears to antagonise the androgenizing and defeminizing effects of testosterone.

5-Hydroxytryptophan↗
PubMed1985

The flexible budget process--a tool for cost containment.

This past year the authors have been using a new tool to examine and monitor their laboratory's expenditures. Called "flexible budgeting," this process has been used to analyze the cost behavior of all operating expenses, establish budget levels for different levels of activity, and monitor activity based on relative cost rather than simply the number of tests performed. The authors' experience has shown that this tool provides much more information than previous procedures. However, better methods need to be developed for monitoring expenditures so that this information can be used effectively.

Budgets↗
PubMed1983

Antibody production to milk proteins in the jejunal mucosa of children with Cow's milk protein intolerance.

A direct immunofluorescent technique with fluorescein-labeled antigens was used to examine the jejunal mucosa for specific antibody reduction in 23 children aged 2--25 months referred for diagnostic biopsy. Plasma cells containing antibodies to beta-lactoglobulin (beta LG) or bovine serum albumin (BSA) were present in 11 of 16 biopsies from patients with cow's milk protein intolerance (CMPI) but only one of eight controls, all on a diet containing cow's milk. Antibody-containing cells (ACC) constituted approximately 0.5--5% of the total (IgA + IgM) plasma cell population. Their presence did not correlate with either histologic abnormality or IgA plasma cell count. Double immunofluorescence with rhodamine-labeled antigens and fluorescein-labeled class-specific anti-human immunoglobulin sera showed the ACC to be approximately 70% IgA cells and 30% IgE cells.

Animals↗