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Biomedical subjects

M M Johnson

Publications and source records attributed to M M Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1995

The isolation and characterization of non-typeable Haemophilus influenzae from the sputum of adult cystic fibrosis patients.

The role of non-typeable Haemophilus influenzae in cystic fibrosis (CF) remains unclear. We wanted, therefore, to determine the presence and characteristics of non-typeable H. influenzae in sputum samples from patients with CF. In order to do this, we have assessed sputum samples from 55 consecutive clinically stable patients seen routinely at an adult CF out-patient clinic. Quantitative bacterial culture was performed using a selective media containing cefsoludin, and isolates were characterized by biotyping and outer membrane protein profile analysis. In 17 (30%) of these samples, non-typeable H. influenzae was isolated and was present in similar viable numbers (mean 7.7 x 10(8) colony-forming units (cfu).mL-1; SEM 3.1) to Pseudomonas aeruginosa (mean 8 x 10(8) cfu.mL-1: SEM 2.4). All non-typeable H. influenzae isolates recovered were beta-lactamase negative and sensitive to a range of antibiotics. Several biotypes and outer membrane protein profiles were observed, with no apparent association between these two phenotypic characteristics. The study showed that large numbers of non-typeable H. influenzae are often present in sputum from adult patients with CF. Further longitudinal studies of outer-membrane protein profile analysis are required to determine the dynamics of non-typeable H. influenzae colonization in individual patients and the clinical significance.

Adolescent↗
PubMed1995

In vivo study of indomethacin in bronchiectasis: effect on neutrophil function and lung secretion.

Bronchiectasis is associated with sputum containing high levels of the proteolytic enzyme elastase, which is thought to be involved in the pathogenesis of the disease. Agents which inhibit neutrophil function and interfere with neutrophil elastase release may have a beneficial effect on the development and progression of such diseases. We have studied the effects of the nonsteroidal anti-inflammatory agent indomethacin on neutrophil function in nine patients with clinically stable bronchiectasis. All patients remained clinically stable during the study. We observed a significant reduction in peripheral neutrophil chemotaxis to 10 nmol.L-1 N-formyl-methionyl-leucyl-phenylalanine (FMLP) from a mean of 19.86 (SEM 1.35) to 8.46 (0.68) cells.field-1 after 4 weeks of therapy. There was also a significant reduction in fibronectin degradation both by resting and FMLP-stimulated neutrophils, from a mean of 1.90 (0.19) micrograms x 3 x 10(5) cells at the start of therapy to 0.87 (0.08) micrograms after 4 weeks, and from 3.17 (0.35) micrograms to 1.48 (0.05) micrograms, respectively. There was no effect on spontaneous or stimulated superoxide anion generation by neutrophils. Despite the marked changes in peripheral neutrophil function, no adverse effect was observed on viable bacterial load in the bronchial secretions. In addition, there was no difference in sputum albumin, elastase or myeloperoxidase levels, and only minor changes in the chemotactic activity of the sputum. These results suggest that nonsteroidal anti-inflammatory agents have a major effect on peripheral neutrophil function but do not appear to have an adverse effect on bacterial colonization of the airways.

Adult↗
PubMed1994

Detection of hepatocellular carcinoma-specific alpha-fetoprotein by isoelectric focusing.

BACKGROUND: Serum alpha-fetoprotein (AFP) is elevated in up to 80% of patients with hepatocellular carcinoma (HCC). Modestly raised AFP levels (10-400 ng/ml) are also found in patients with nonmalignant liver diseases. In the present study, isoelectric focusing of AFP was used to differentiate the AFP found in patients with HCC. METHODS: To establish the assay conditions, isoelectric focusing was performed on sera from 14 patients with HCC and 13 with nonmalignant liver diseases. Sera was also analyzed under coded conditions from 16 patients with HCC, 14 with chronic active hepatitis (CAH), and 6 with cirrhosis to determine the specificity and sensitivity of the assay in the diagnosis of HCC. RESULTS: Isoelectric focusing of sera from patients with HCC and various non malignant liver diseases identified AFP variants (AFP I-IV). All 14 patients with HCC had AFP variants I and III, and 7 of the 14 also had variant IV. When analyzed in the coded study 13 of the 16 cases of HCC were predicted correctly by the presence of AFP variants III or III and IV. AFP bands III and IV were not discernible in 12 of the 14 patients with CAH and 4 of the 6 with cirrhosis. CONCLUSION: Isoelectric focusing of sera from patients with HCC and nonmalignant liver disease identified two AFP variants apparently specific for HCC. In the setting of borderline elevation of AFP, this technique has a sensitivity of 81% and specificity of 85% for detecting the presence of bands III or IV and may prove suitable for use in a routine laboratory as a screening assay.

Carcinoma, Hepatocellular↗
PubMed1994

Studies on the platelet surface-associated von Willebrand factor.

The contribution of platelets to the prevention and control of bleeding depends not only on the plasma and vessel wall von Willebrand (vW) factor, but also on the vW factor originating from platelets. Although platelet vW factor is mainly stored in the alpha-granules, small amounts of vW factor have been detected on the platelet surface under conditions without direct stimulation. This communication focuses on the small amount of vW factor associated with the surface of platelets. EDTA-washed platelets in a calcium-free medium containing prostaglandin E1 (PGE1) were exposed to anti-vW factor F(ab')2 fragments. The platelet-associated anti-vW factor antibodies were separated from the free fragments by gel chromatography. Normal platelets were compared to platelets from patients with Bernard Soulier syndrome, Glanzmann's thrombasthenia, and Hermansky-Pudlak syndrome. These experiments showed that, in the absence of extracellular calcium, vW factor can be detected on the surface of washed platelets independent of glycoproteins Ib and IIb-IIIa, and despite markedly reduced intracellular calcium content. This particular platelet surface expression of vW factor is probably the result of disturbing the platelet during the in vitro manipulation. von Willebrand factor is an extremely important element in the multiple molecular interactions required to stop and anchor the platelet in areas of high flow rates. Mechanical perturbation of platelets leading to surface expression of the vW factor helps increase its availability for such critical interactions.

Albinism, Oculocutaneous↗
PubMed1994

Sputum and serum pharmacokinetics of loracarbef (LY163892) in patients with chronic bronchial sepsis.

Sputum and serum pharmacokinetics of loracarbef (LY163892) were performed in 19 patients with purulent bronchiectasis. Nine of the patients received 200 mg twice daily and ten patients, 400 mg twice daily, for a total of 14 days. beta-Lactamase activity was measurable in the lung secretions of all 19 patients at the start of therapy. Mean peak serum concentrations of 11.7 mg/L (S.E.M. 1.7) were recorded at 1 h after administration of 200 mg doses on day 2 of therapy and were 18.5 mg/L (S.E.M. 1.9) at 1.5 h in the 400 mg group. Loracarbef was shown to penetrate lung secretions even in the presence of beta-lactamase activity. Mean peak sputum concentrations were achieved between 2 and 4 h following dosing and were 0.2 mg/L (S.E.M. 0.05) in the 200 mg group and 0.4 mg/L (S.E.M. 0.08) in the 400 mg group. On days 7 and 14 of therapy, sputum loracarbef concentrations were similar 4 h after the morning dose (0.23 mg/L following 200 mg; 0.35 mg/L after 400 mg). These concentrations were approximately 2% of the peak serum concentration and penetration into lung secretions is similar to other beta-lactams.

Adult↗
PubMed1993

Thinking about strategies during, before, and after making a decision.

Two studies examined the impact of think-aloud and self-report instructions on the decision-making performance of young and older adults. Findings from Study 1 indicated that think-aloud instructions increased total time to decision for young and older adults but did not otherwise affect decision-making processes. Counter to predictions, the only significant interaction effect indicated that young adults in the think-aloud condition more frequently rechecked information than older adults. Findings from Study 2 confirmed the nonreactive nature of self-report methods. Despite potential age-related decrements in cognitive function, differences in functioning are not compounded and cannot be explained by the think-aloud or self-report instructions used by cognitive aging researchers.

Adult↗
PubMed1993

Ongoing ischemic pain as a workload indexed by P3 amplitude and latency in real-versus feigned-pain conditions.

We tested four independent groups: real pain, real pain/tracking, feigned pain, and feigned pain/tracking. After baseline (auditory oddball task only, .8/.2), the real pain groups had an ischemia cuff applied, which generated intense pain after 14 min. The pain feigners were instructed to simulate pain. The oddball task was repeated during low pain (6 min following cuff application) and during high pain (7-15 min following application). Real pain ratings were affected by low versus high pain and by tracking (reporting pain regularly), which elevated ratings. Nontracking feigned- and real-pain subjects differed in oddball-evoked P3 amplitude and latency during high pain. Oddball P3 amplitude decreased and latency increased from real low pain to high pain. Tracked but not untracked real low pain affected oddball P3 amplitude. Real and feigned pain-tracking subjects did not differ in P3 amplitude. P3 latency differed between real-pain and feigning subjects during low-pain tracking. A 91% individual hit rate (real vs. feign) obtained.

Adolescent↗
PubMed1993

Technical note: an improved method to quantify nonesterified fatty acids in bovine plasma.

Nonesterified fatty acids (NEFA) are measured routinely in the study of nutrition and growth physiology. To improve the efficiency with which this variable is measured, a two-reaction, enzymatic-based assay was adapted and validated to quantify NEFA in bovine blood plasma using 96-well microtiter plates. The effects of incubation time, temperature, and of sample volume were examined in addition to possible interfering substances, recovery, reagent stability, and range of linearity. Incubation for 30 min at 21 degrees C for each of the two reactions resulted in maximal slope and r2 values (1.94 and .999, respectively). Percentage of recovery was 107% when using 5 microL and 100% when using 10 microL of heparinized bovine plasma in the assay. Uniform linear standard curves (r2 > .99) were obtained using reagents stored at 4 degrees C for 9 d. An equal volume of 1 mM acetate, propionate, valerate, and butyrate added to plasma did not affect results. The assay was linear from 125 to > 1,000 microEq/L. Intra- and interassay CV for the 5-microL sample volume were 3.6 and 3.7%, respectively. This modified assay provides results comparable to the standard assay yet reduces reagent and labor requirements and increases sample capacity.

Animals↗
PubMed1992

Oddball-evoked P300-based method of deception detection in the laboratory. II: Utilization of non-selective activation of relevant knowledge.

We used a deception paradigm modeled on the type used for pre-employment screening procedures. Our novel dependent measure was P300 amplitude. Event-related potentials (ERPs) were recorded while subjects were presented with a list of eight antisocial acts one at a time, and one target-response phrase to which a 'yes' button press was required. Subjects were instructed to try to escape detection during the ERP test if they were guilty of any of the acts. After the ERP test, ground truth was established by the completion of an innocent/guilty check list of antisocial acts under perceived anonymous conditions tending to favor honest responding. Subjects were classified as innocent (n = 14) or guilty (n = 17) based on their check list response to the relevant act 'Used Falsified ID'. When comparing the P300 amplitudes in response to the relevant and to another act, we found that most group analyses revealed significant differences between guilty and innocent subjects. The subjects were also individually classified by a 3-step algorithm which involved: (1) a bootstrap amplitude test that compared the bootstrapped amplitudes of the P300s to the relevant and to another act; (2) relevant-to-target item P300 amplitude ratios; and (3) relevant act P300 amplitudes. Overall, the algorithm yielded 87% accuracy. The present study was intended to be an advance over our previous study (Rosenfeld, et al., 1991), in which we correctly classified 89% of the subjects using a similar P300-based deception detection paradigm. However, the possible confounding limitation of that study was that subjects had to complete an innocent/guilty check list of their antisocial acts prior to the ERP test. The present study investigated the accuracy of the P300-based test when subjects did not admit or selectively rehearse their guilt of the relevant act prior to the ERP test.

Electrodes↗
PubMed1991

Using life histories to individualize nursing home staff attitudes toward residents.

This study assesses the impact of life histories on nursing home staff attitudes. Nurse's aides at two institutions answered questions about their experience and knowledge of aging, and rated nursing home residents on a semantic differential (attitude) scale. Aides received one of two versions of an anonymous resident's medical chart, identical except for the inclusion of a one-page life history. Controlling for individual differences such as prior work experience and knowledge about aging, staff reviewing the chart with the life history rated that resident as more instrumental, autonomous, and personally acceptable than staff who reviewed the chart without the life history.

Attitude of Health Personnel↗
PubMed1990

Age differences in decision making: a process methodology for examining strategic information processing.

This study explored the use of process tracing techniques in examining the decision-making processes of older and younger adults. Thirty-six college-age and thirty-six retirement-age participants decided which one of six cars they would purchase on the basis of computer-accessed data. They provided information search protocols. Results indicate that total time to reach a decision did not differ according to age. However, retirement-age participants used less information, spent more time viewing, and re-viewed fewer bits of information than college-age participants. Information search patterns differed markedly between age groups. Patterns of retirement-age adults indicated their use of noncompensatory decision rules which, according to decision-making literature (Payne, 1976), reduce cognitive processing demands. The patterns of the college-age adults indicated their use of compensatory decision rules, which have higher processing demands.

Adolescent↗