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Biomedical subjects

L J Johnson

Publications and source records attributed to L J Johnson.

At least 19 recordsLinked to original sources
PubMed2000

Optical light scatter imaging of cellular and sub-cellular morphology changes in stressed rat hippocampal slices.

Optical imaging, such as transmission imaging, is used to study brain tissue injury. Transmission imaging detects cellular swelling via an increase in light transmitted by tissue slices due to a decrease in scattering particle concentration. Transmission imaging cannot distinguish sub-cellular particle size changes from cellular swelling or shrinkage. We present an optical imaging method, based on Mie scatter theory, to detect changes in sub-cellular particle size and concentration. The system uses a modified inverted microscope and a 16-bit cooled CCD camera to image tissue light scatter at two angles. Dual-angle scatter ratio imaging successfully discriminated latex microsphere suspensions of differing sizes (0.6, 0.8, 1 and 2 microm) and concentrations. We applied scatter imaging to hippocampal slices treated with 100 microM N-methyl-D-aspartate (NMDA) to model excitotoxic injury or -40 mOsm hypotonic perfusion solution to cause edema injury. We detected light scatter decreases similar to transmission imaging in the CA1 region of the hippocampus for both treatments. Using our system, we could distinguish between NMDA and hypotonic treatments on the basis of statistically significant (P<0.0003) differences in the scatter ratio measured in CA1. Scatter imaging should be useful in studying tissue injuries or activity resulting in brain tissue swelling as well as morphological changes in sub-cellular organelles such as mitochondrial swelling.

Animals↗
PubMed2000

Gambling behavior of Louisiana students in grades 6 through 12.

OBJECTIVES: The prevalence of problem and gambling behavior, the average age of onset of gambling behavior, and the co-occurrence of gambling disorder with substance use were determined in the Louisiana student population grades 6 through 12. METHODS: A stratified randomized sample of 12,066 students in Louisiana schools during the 1996-1997 school year was surveyed about gambling behavior using the South Oaks Gambling Screen--Revised for Adolescents (SOGS-RA). RESULTS: Fourteen percent of the students never gambled, 70.1 percent gambled without problems, 10.1 percent indicated problem gambling in the past year (level 2 according to the SOGS-RA), and 5.8 percent indicated pathological gambling behavior in the past year (level 3). Weekly or more frequent lottery play was reported by 16.5 percent. The average age of onset of gambling behavior was 11.2 years. Fifty-nine percent of the students with problem and pathological gambling behavior reported frequent alcohol and illicit drug use. CONCLUSIONS: A significant minority of Louisiana students in grades 6 through 12-15.9 percent--acknowledged gambling-related symptoms and life problems. The association of problem and pathological gambling with use of alcohol, tobacco, and marijuana provides preliminary support for the inclusion of gambling among other adolescent risk behaviors.

Adolescent↗
PubMed2000

Daily smoking by Louisiana students: sixth through twelfth grades, 1996-1997.

OBJECTIVES: We sought to determine the prevalence of daily smoking in Louisiana in grades 6 through 12 and to compare Louisiana students' daily smoking to that of national student and Louisiana adult rates. METHODS: A statewide, randomized, stratified classroom-based survey of 11,736 subjects was done for the school year 1996-1997. RESULTS: We found that 17.3% of sixth grade students smoked daily, increasing to 36.1% in twelfth grade. Native American (43.7%), white (37.8%), and public school (28.5%) students had the highest rates of daily smoking. Males and females smoked at similar rates. Louisiana students in grades 8, 10, and 12 smoked daily at much higher rates (331%, 193%, and 146%, respectively) than comparable national samples. In 1997, Louisiana students smoked daily at higher rates than did Louisiana adults (28.9% vs 24.6%), primarily due to higher rates of smoking in student females (27.1%) compared to adult females (20.4%). CONCLUSIONS: Student smoking in Louisiana is a significant public health problem.

Adolescent↗
PubMed2000

Gambling in the south: implications for physicians.

Three historical cycles of legalized gambling have occurred in the South. Currently, every southern state has legalized some form of gaming. Adult past-year prevalence rates of problem gambling in southern states are within the national range. Higher prevalence rates occur in states with casinos and multiple forms of legalized gambling. States with lotteries have higher prevalence rates of adolescent problem gambling. Problem gambling can cause stress-induced physical diseases and psychiatric symptoms in gamblers and their families. Physicians can reduce personal, family, and social costs of problem gambling through increased awareness, strategic screening, and early intervention. Treatment approaches include inpatient treatment centers, self-help fellowship groups, and cognitive-behavioral and addiction-based psychotherapies. Although no standard pharmacologic treatments for gambling disorders exist, use of selective serotonin re-uptake inhibitors is under investigation. Referral resources are available to physicians in states with state-funded treatment programs for problem gamblers and/or state councils for problem gambling.

Adolescent↗
PubMed1999

Warfarin responses in total joint and hip fracture patients.

Warfarin is considered as a narrow therapeutic drug-an agent for which small changes in dosage can lead to significant changes in response. The precision of warfarin treatment is especially relevant in an acute-care setting. In this study, we examined the effect of various risk factors on warfarin response in the early postoperative period after total joint arthroplasty and hip fracture fixation. A total of 260 patients placed on warfarin for thrombosis prophylaxis were retrospectively studied. Risk factors for warfarin sensitivity include age 80 years or older and hip fracture fixation. Patients aged 80 years or older who had hip fracture fixation were 4.7 times more likely to experience an international normalized ratio (INR) at or greater than 4.0 than other patients (therapeutic target range of INR, 1.8-2.2). The largest subtherapeutic risk group in this study were men weighing 180 lb or more. They were 5.7 times less likely to achieve an INR of 1.6 than the other patients. Factors such as body weight, age, and gender should be considered when ordering warfarin therapy. Current hospital warfarin sliding scales should be reviewed for their efficacy to ensure that the target outcome is achieved.

Aged↗
PubMed1999

The snoring spectrum: acoustic assessment of snoring sound intensity in 1,139 individuals undergoing polysomnography.

STUDY OBJECTIVES: To quantify the snoring sound intensity levels generated by individuals during polysomnographic testing and to examine the relationships between acoustic, polysomnographic, and clinical variables. DESIGN: The prospective acquisition of acoustic and polysomnographic data with a retrospective medical chart review. SETTING: A sleep laboratory at a primary care hospital. PARTICIPANTS: All 1,139 of the patients referred to the sleep laboratory for polysomnographic testing from 1980 to 1994. INTERVENTIONS: The acoustic measurement of snoring sound intensity during sleep concurrent with polysomnographic testing. MEASUREMENTS AND RESULTS: Four decibel levels were derived from snoring sound intensity recordings. L1, L5, and L10 are measures of the sound pressure measurement in decibels employing the A-weighting network that yields the response of the human ear exceeded, respectively, for 1, 5, and 10% of the test period. The Leq is a measure of the A-weighted average intensity of a fluctuating acoustic signal over the total test period. L10 levels above 55 dBA were exceeded by 12.3% of the patients. The average levels of snoring sound intensity were significantly higher for men than for women. The levels of snoring sound intensity were associated significantly with the following: polysomnographic testing results, including the respiratory disturbance index (RDI), sleep latency, and the percentage of slow-wave sleep; demographic factors, including gender and body mass; and clinical factors, including snoring history, hypersomnolence, and breathing stoppage. Men with a body mass index of > 30 and an average snoring sound intensity of > 38 dBA were 4.1 times more likely to have an RDI of > 10. CONCLUSIONS: Snoring sound intensity levels are related to a number of demographic, clinical, and polysomnographic test results. Snoring sound intensity is closely related to apnea/hypopnea during sleep. The noise generated by snoring can disturb or disrupt a snorer's sleep, as well as the sleep of a bed partner.

Adult↗