Search PubMed⌕ Search

Biomedical subjects

B W Johnson

Publications and source records attributed to B W Johnson.

16 recordsLinked to original sources
PubMed1990

Effects of inflammation and aqueous tear film deficiency on conjunctival morphology and ocular mucus composition in cats.

An experimental model of keratoconjunctivitis sicca (KCS) was produced by removing the lacrimal gland and the gland of the third eyelid from the left eye of 6 cats. The right eye of each cat was left intact and used as a control. After 2 weeks, cats were euthanatized and the central portion of the upper eyelid from both eyes of each cat was excised. Histologic sections were stained with either hematoxylin and eosin or with a battery of biotinylated lectins including concanavalin A (conA), soybean agglutinin (SBA), wheat germ agglutinin (WGA), succinylated wheat germ agglutinin (S-WGA), Ulex europaeus agglutinin I (UEA), Dolichos biflorus agglutinin (DBA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA), and PNA pretreated with neuraminidase. Consistent differences in histologic features were not observed between conjunctivas with KCS and control conjunctivas. A variable degree of mononuclear cell infiltration of the substantia propria was observed in control conjunctivas and those with KCS. In both groups, conjunctival goblet cell density decreased and epithelial stratification increased as the degree of submucosal inflammatory cell infiltration increased. Lectin binding sites for DBA, WGA, S-WGA, UEA, PNA, and PNA pretreated with neuraminidase were detected on conjunctival goblet cells of conjunctivas with KCS and control conjunctivas. The mucus/glycocalyx layer of conjunctival epithelial cells in both groups of conjunctivas bound lectins RCA, WGA, UEA, and conA, but inconsistently bound S-WGA. In both groups, DBA principally bound to the mucus layer overlying normal epithelium, whereas PNA pretreated with neuraminidase consistently bound to the mucus layer of stratified epithelial surfaces free of goblet cells. Binding of SBA to goblet cells and the mucus/glycocalyx layer was variable.

Animals↗
PubMed1988

Intraocular Cuterebra in a cat.

A cat had sudden onset of unilateral corneal edema, fibrin in the anterior chamber, uveal inflammation, and retinal dysfunction. A dead dipteran fly larva was removed surgically from the anterior chamber and was identified as an early instar of a Cuterebra sp.

Animals↗
PubMed1988

Topographic distribution of the 40 Hz auditory evoked-related potential in normal and aged subjects.

Galambos, Makeig and Talmachoff (1981) described what they called the 40 Hz event-related potential (ERP). This steady-state response is an EEG following response to repetitive auditory stimulation which becomes sinusoidal in form and maximal in amplitude at rates between 35 and 45 Hz. The present study was designed to examine the scalp topography of the 40 Hz ERP in order to complement previous magnetoencephalographic studies which implicate auditory cortex in the generation of the response. In addition, this study was designed to collect normative data on an aged sample in order to assess the effects of aging on the response. 40 Hz ERP's were recorded from a group of seven audiometrically and neurologically normal elderly subjects (mean age = 69.6 years) and a younger group of five normal adults (mean age = 38.0 years), using 1000 Hz tones presented binaurally at 40 per second. A 21 channel recording system was used to obtain a comprehensive picture of the scalp distribution of the response. Recorded ERP's were Fourier transformed to enhance the signal-to-noise ratio. No significant differences were found in phase or amplitude of the 40 Hz ERP between the two age groups, indicating that the normal aging process does not have an effect on this response. Topographic maps of the 40 Hz ERP showed reversals of electrode potential in temporal regions, supporting an interpretation of bilateral sources in temporal cortex. The data presented in this study complement previous studies of the 40 Hz event-related magnetic field and support the position that temporal cortex is involved in the generation of the response.

Acoustic Stimulation↗
PubMed1988

Assessment of stress during periodontal surgery with intravenous sedation and with local anesthesia only.

Ten patients with moderate to advanced periodontal disease were subjected to two similar periodontal surgical procedures. Each patient received either intravenous conscious sedation with local anesthesia or local anesthesia only. The stress-reducing effects of a conscious sedation regimen consisting of pentobarbital, meperidine, and diazepam were evaluated in these patients. Stress was evaluated by monitoring changes in serum cortisol, human growth hormone, and vital signs. Blood samples were obtained at 15- to 30-minute intervals throughout each procedure and were evaluated for serum cortisol and growth hormone. The conscious sedation group had significantly lower serum cortisol levels and lower systolic blood pressure, indicating that the patients having periodontal surgery with conscious sedation experienced reduced stress. Physiologic stability was maintained for each patient, indicating that this conscious sedation regimen can be used to reduce measurable parameters of stress that patients develop during periodontal surgery.

Anesthesia, Dental↗
PubMed1988

Diagnosis and management of angioid streaks.

Angioid streaks are asymptomatic breaks in Bruch's membrane developing later in life. Secondary macular degeneration and other fundus abnormalities often accompany their development. Angioid streaks are frequently associated with systemic diseases such as pseudoxanthoma elasticum, Paget's disease of bone, and the sickle cell hemoglobinopathies. The clinical manifestations of angioid streaks, related fundus changes, and these three systemic disorders are discussed as well as principles of treatment and management. Two case reports are presented which illustrate some of the important characteristics of angioid streaks.

Aged↗
PubMed1987

An adaptable optimal controller for electric wheelchairs.

A microcomputer-based optimal control system for electric wheelchairs is presented. As the weight of a wheelchair is generally small compared to that of a user, the user's actual weight can have a tremendous impact on the dynamics of the wheelchair. The velocity feedback controller presented here was designed to give an optimal response for all users by incorporating a measure of the individual user's weight into the control algorithm. This allows optimal control of the motor velocities while assuring the constant stability of the system. Control of the system is managed by a modified proportional-integral-derivative (PID) controller, and the adaptability is handled by use of variable-structure control. The factors and considerations involved in such a system are identified, as are the advantages and disadvantages of the particular control strategy used. Experimental results are presented.

Microcomputers↗
PubMed1985

Experimental wound healing: increased breaking strength and collagen synthetic activity in abdominal fascial wounds healing with secondary closure of the skin.

Delayed primary closure or secondary closure of skin and subcutaneous fat in contaminated laparotomy incisions virtually eliminates the risk of wound abscess in clinical practice. Incisional hernias rarely develop in these wounds. This experimental study offers a possible explanation. Longitudinal incisions in the linea alba of female Wistar rats healed under skin incisions which were either sutured ('closed' subgroup) or left to close by secondary intention ('open' subgroup). Postoperative breaking strengths and collagen contents (measured as hydroxyproline) were studied at intervals of 3-120 days. Measurable strength developed by 5 days, at which time 'open' subgroup wounds were found to be weaker and to have less collagen. At all other times, however, 'open' subgroup wounds were stronger, a property which could be ascribed at earlier, but not at later, periods (42 or 120 days), to a higher content and concentration of collagen. At 3 days the rate of collagen production was significantly (P less than 0.025) lower in 'open' than in 'closed' subgroup wounds but the converse was true at 6 and 9 days (P less than 0.025), thus accounting for the changes in biomechanical properties. It is suggested that initially the stimulus for collagen synthesis is greater in the 'open' wounds and this leads to the development of a collagenous structure which is better adapted to resist tensile forces.

Abdominal Muscles↗
PubMed1983

In vitro method for detecting precipitation of parenteral formulations after injection.

Many injectable formulations currently on the market, including diazepam and alprazolam, utilize one or more cosolvents to solubilize the active constituents. On injections into an aqueous medium, some of these components tend to precipitate. A simple procedure is described for measuring the degree of precipitation that occurs when a solubilized drug is injected. This in vitro technique was used to show that alprazolam injection shows less precipitation than diazepam injection under all tested conditions, and that the precipitation observed with diazepam can be controlled by ensuring that the formulation is injected very slowly. This simple technique also can be used during preformulation development to evaluate the relative potential for precipitation of various formulations.

Alprazolam↗
PubMed1982

Primary and secondary healing in infected wounds. An experimental study.

The beneficial effects of delayed closure of contaminated wounds are recognized, but not well defined. Rats with abdominal incisions were infected with Staphylococcus aureus or Escherichia coli and then subgrouped for primary or secondary healing. Noninfected rats served as controls. Between seven and 119 days later, the wounds were subjected to breaking-strength determination, hydroxyproline analysis, and light and scanning electron microscopy. In the controls, secondary closure gave stronger wounds than primary closure. In those infected with S aureus the wounds were stronger than in the primary-closure control group, regardless of the closure method. Of the E coli-infected wounds those primarily closed were weaker than those secondarily closed. Secondary closure gave infected wounds fewer complications. Biochemical and microscopic examination did not explain these findings.

Abdominal Muscles↗