Search PubMed⌕ Search

Biomedical subjects

L J Johnson

Publications and source records attributed to L J Johnson.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1998

Gambling behavior of adolescents in residential placement in northwest Louisiana.

BACKGROUND: The rapid expansion of legalized gambling in the United States necessitates evaluation of its impact on vulnerable populations, especially adolescents. METHODS: Gambling behavior in 135 adolescents in residential placement in northwestern Louisiana was measured using the South Oaks Gambling Screen-Revised for Adolescents. RESULTS: During the past year, 41% of these adolescents reported minimal problems with gambling, 21% reported level 2 or problem gambling, and 38% reported level 3 or pathologic gambling. In this population, the first drink of alcohol, the first cigarette, and the first experience with gambling began on average at 11 years of age, with the first use of marijuana and the first episode of alcohol intoxication occurring a year later. CONCLUSION: The level 2 rate of gambling exceeded the upper extreme of the adolescent community sample range, and the level 3 rate was approximately six times the reported level 3 community prevalence rate for adolescents. Residential placements sites should be considered when developing prevention programs for gambling disorders.

Adolescent↗
PubMed1997

The role of cytokines in the behavioral responses to endotoxin and influenza virus infection in mice: effects of acute and chronic administration of the interleukin-1-receptor antagonist (IL-1ra).

Following infection with influenza virus, animals display decreased locomotor activity and feeding behavior and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), induced by the infection. To assess the potential role of IL-1, we tested the ability of a naturally occurring IL-1-receptor antagonist (IL-1ra) to antagonize the changes in feeding behavior induced by IL-1, endotoxin (lipopolysaccharide, LPS), and infection with influenza virus. Feeding behavior was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. Acute injection of IL-1 beta decreased milk intake, but mouse IL-6 and mouse TNF-alpha did not. However, TNF-alpha decreased food pellet intake slightly, especially when it was injected at the beginning of the dark phase. The reductions in milk intake induced by mouse IL-1 beta were largely prevented by IL-1ra pretreatment (100 micrograms/mouse i.p.). The LPS-induced reductions in milk intake were attenuated, but not blocked, by IL-1ra treatment (300 micrograms/mouse). LPS still induced significant decrements in the presence of the antagonist. In influenza virus-infected mice, IL-1ra was administered either by repeated subcutaneous (s.c.) injections, or by continuous s.c. infusion from osmotic minipumps. These IL-1ra treatments produced small, but statistically significant, attenuations of the depression in milk and food pellet intake in the virus-infected mice. In several experiments, IL-1ra treatment increased the survival of influenza virus-infected mice. Thus the attenuation of the hypophagia may have been caused by this IL-1ra-induced increase in survival. The results suggest that IL-1 contributes to sickness behavior induced by LPS and influenza virus infection, but it is not the only factor involved.

Animals↗
PubMed1997

An in vivo analysis of the dimensional changes of the neuroforamen after anterior cervical diskectomy and fusion: a radiologic investigation.

Eighteen patients (11 men, 7 women; average age, 45.5 years) who underwent anterior cervical diskectomy and fusion (ACDF) for the treatment of radiculopathy had preoperative and immediate postoperative computed tomography (CT) scans to measure pre- and postoperative foraminal heights and foraminal areas, preoperative disk space height, and postoperative graft height. The mean foraminal height preoperatively was 0.851 cm; postoperatively, it was 1.01 cm, with a mean percentage increase of 20% (-8.8 to 56.8%). Mean preoperative foraminal area was 37.53 mm2, increasing to a mean of 49.04 mm2 postoperatively with a mean percentage increase of 33% (range, -1.5 to 76.9%). No significant correlations between graft height and change in maximal foraminal height or foraminal area or between changes in foraminal height or area and postoperative symptom relief were found. Although significant increases in foraminal dimensions were seen radiographically after ACDF, these increases were variable and not strongly related to graft height. In addition, the increases in foraminal dimensions were not related to the short-term clinical results of ACDF. This study fails to support the hypothesis that the reliable results of ACDF can be ascribed primarily to indirect decompression of the uncovertebral foramen by disk-space distraction.

Adult↗
PubMed1996

G-protein coupling of muscarinic receptors in adult and neonatal rat submandibular cells.

The submandibular glands of neonatal and adult rats express muscarinic cholinergic receptors. Receptor occupancy initiates signaling through activation of phospholipase C, hydrolysis of inositol phospholipids, and calcium mobilization. The increased cytoplasmic [Ca2+] activates ion transport pathways, resulting in secretion of primary saliva. We have previously shown that muscarinic receptors are present in the gland of neonates and that they couple effectively to inositol trisphosphate production and Ca2+ mobilization but that the monovalent ion transport paths are poorly activated. To characterize age-related differences in signal transduction further, we examined the coupling of muscarinic receptors to G-proteins by determining the effect of GTP on the IC50 for competition by the muscarinic agonist carbachol with the radiolabeled antagonist, 3H-quinuclidinyl benzylate. Data were fit to one-site and two-site models, and in all cases the two-site model provided the better fit. Using the two-site model, a substantial GTP-induced shift from high affinity to low affinity binding was observed in membranes from adults, whereas more of the receptors were already in the low affinity form in the membranes from neonates, and little additional shift was induced by GTP. These results suggest differences in the G-protein coupling of muscarinic receptors in submandibular cells of adult and early postnatal rats that may be associated with differences in the content, affinity, or properties (i.e., posttranslational modifications) of G-proteins as the cells mature.

Age Factors↗
PubMed1996

Muscarinic signalling in submandibular salivary acinar cells of ageing rats.

Muscarinic cholinergic stimulation of submandibular acinar cells results in the activation of Ca(2+)-dependent ion-transport pathways responsible for the secretion of primary saliva. Decreased saliva production is common among elderly people and may compromise oral health with implications for systemic health, nutrition, and quality of life. The density and affinity of muscarinic receptors in the submandibular gland of rats and the Ca2+ responses to stimulation of these receptors in the acinar cells were examined. An increase in the number of receptors and increases in the affinities of the receptors were found as the rats age from 7 weeks to 11 months. However, the coupling of the receptors to the intracellular Ca2+ signals in acinar cell clusters was substantially reduced in the older animals.

Acetylcholinesterase↗
PubMed1996

Renal transplant nuclear tomography using Tc-99m MAG3.

In this study, the authors performed SPECT imaging on 12 renal transplant patients immediately after a routine planar study demonstrated tubular stasis. The stasis allowed the authors to obtain good quality tomograms on all of them. In five patients, the findings on the planar and SPECT studies were identical. In five patients, there was decreased upper pole activity on planar images and SPECT imaging differentiated between attenuation (4 patients) and cortical thinning (1 patient). In the remaining two patients, the SPECT images showed unanticipated information. It is not yet clear if this new information is of clinical value. It was concluded that diagnostic quality nuclear tomograms in renal transplant patients with tubular stasis can be easily and consistently obtained.

Humans↗
PubMed1996

A biomechanical study of torque and accuracy of halo pin insertional devices.

The purpose of the present study was to assess the accuracy and repeatability of the torque achieved with a variety of devices used for the insertion of halo pins. We found that equivalent devices from the same manufacturer did not reliably achieve the same torque, that the same device used by different surgeons did not reliably achieve the same torque, and that the devices achieved varying levels of accuracy and repeatability. The proportion of trials in which the achieved torque was within +/- 10 per cent of the intended torque averaged 64 per cent (range, less than 1 to 100 per cent). Our data suggest that the insertion of halo pins with use of most currently available torque-setting devices is an inherently inaccurate process.

Biomechanical Phenomena↗