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Biomedical subjects

J L Taylor

Publications and source records attributed to J L Taylor.

At least 91 records · Page 5Linked to original sources
PubMed1996

Endothelial barrier function and Na+/K(+)-ATPase pump density in herpetic stromal disease.

PURPOSE: Corneal edema is a significant component of the various forms of herpes simplex virus type 1 (HSV-1)-induced stromal disease. Maintenance of corneal thickness, a reflection of corneal hydration, depends on a physical barrier formed by endothelial cell-cell junctions and by the activity of Na+/K(+)-ATPase pumps that regulate ion flux and thus influence water movement through this cell layer. These functions were measured in corneas with increased corneal thickness caused by HSV-1-induced stromal disease to determine their contribution to the pathogenesis of the edema. METHODS: Stromal disease with corneal edema was induced in rabbits by intrastromal injection of the RE strain of HSV-1. At various times after infection, during the development of and recovery from stromal disease, endothelial barrier function and Na+/K(+)-ATPase pump sites were measured in excised rabbit corneas. RESULTS: The endothelial permeability coefficient, Ktrans, for 14C-dextran, 3H-inulin, and 14C-mannitol, were not altered significantly during periods of maximal corneal edema and stromal disease. Endothelial Na+/K(+)-ATPase pump density, as measured by ouabain binding, showed a statistically significant (P < 0.05) decrease in HSV-1-infected corneas during peak edema compared to mock antigen-injected or uninjected control corneas. Pump density returned to baseline values by 24 days after infection, concurrent with the resolution of corneal edema. CONCLUSIONS: These results indicate that corneal endothelial barrier function was not altered in this form of HSV-1-induced stromal edema; however, pump density was reduced significantly.

Animals↗
PubMed1996

A pharmacoeconomic model of divalproex vs. lithium in the acute and prophylactic treatment of bipolar I disorder.

BACKGROUND: Divalproex and lithium are the two most rigorously studied pharmacologic treatments for acute mania in bipolar I disorder in randomized, controlled trials. The differences between the drugs in their time course of onset, predictors of response, and side effects have potentially important pharmacoeconomic implications. METHOD: Utilizing data from published studies, the University of Cincinnati Mania Project, and a consensus panel of psychiatrists, we developed a decision-analytic model to estimate the costs of treating patients with bipolar I disorder, acutely and prophylactically, for 1 year with divalproex or lithium. RESULTS: In the overall group of patients with bipolar I disorder, initial treatment with divalproex led to costs that were 9% lower than costs for initial treatment with lithium. Cost savings associated with divalproex were greatest for patients with mixed mania and rapid cycling, whereas cost savings for patients with classic mania were greater for lithium. CONCLUSION: According to the decision-analytic model developed in this study, divalproex, possibly because of a more rapid rate of antimanic activity associated with oral loading, is a less costly treatment than lithium in the acute and prophylactic treatment of patients with bipolar I disorder over 1 year.

Acute Disease↗
PubMed1996

Alcohol elimination and simulator performance of male and female aviators: a preliminary report.

OBJECTIVES: In this preliminary study of alcohol effects on aviators' flight simulator performance, we addressed some methodological issues regarding possible gender-related differences in response to alcohol. METHODS: Subjects were 11 male and 12 female general aviation pilots, ages 21-40. Subjects received 8 h of training before they were tested with alcohol. On the alcohol test day they were tested before drinking, while intoxicated (target BAC of 0.08%), and 8 h after drinking. RESULTS: The average, observed peak BAC readings for men and women were within 0.003% of each other. We observed faster disappearance rates for women such that women reached the FAA cutoff of 0.04% approximately 1 h before men, on average. Compared to predrink performance, there was a significant decrement in simulator performance during acute intoxication, but not 8 h after drinking. There were no significant gender differences in performance before or after drinking alcohol. Slower rates of alcohol elimination were associated with larger performance changes 8 h after drinking. This is the first report to our knowledge suggesting a possible relation between alcohol elimination rate and change in performance after drinking alcohol. CONCLUSIONS: A 12.5% dose reduction for women appears to be adequate for achieving comparable peak BAC's for male and female groups. Future studies using measures of circadian rhythmicity in conjunction with pharmacokinetic and performance measures could potentially shed light on differences in subjects' acute and delayed responses to alcohol.

Adult↗
PubMed1995

Ipsilateral cortical stimulation inhibited the long-latency response to stretch in the long finger flexors in humans.

1. Transcranial magnetic stimulation over the motor cortex of one hemisphere is known to decrease the excitability of the motor cortex of the other hemisphere. We investigated the effect of this interhemispheric or transcallosal inhibition of the motor cortex on the reflex response to stretch in the long flexors of the fingers in human subjects. 2. Stretch of the long finger flexors, through extension of the proximal interphalangeal joints with a torque pulse, resulted in a reflex EMG response with short- and long-latency components. Magnetic stimulation was applied over the motor cortex ipsilateral to the muscles being stretched. When a magnetic shock but not stretch was given, a decrease in background EMG in the ipsilateral finger flexors occurred at a latency of 33 +/- 6.2 ms after the stimulus and with a duration of 25 +/- 8.5 ms. 3. If the magnetic shock and the stretch were given at appropriate interstimulus intervals, the long-latency stretch reflex (LLSR) showed inhibition in all subjects. LLSR was reduced to 49.2 +/- 19% (S.D.; n = 9) of the area of the control response. 4. The LLSR did not act as a single event in response to the magnetic shock. That is, part of the LLSR could be reduced in amplitude while the remainder was unaffected. The reduction in LLSR had an onset latency of 27 +/- 3.8 ms after the magnetic stimulus and a duration of 29-55 ms. Inhibition was only obvious when this interval after the magnetic stimulus coincided with the LLSR. 5. In most subjects the short-latency stretch reflex (SLSR) also showed some inhibition (83.4 +/- 11.2% of the control). However, this was less than the effect on the LLSR in all subjects. 6. The site of stimulation, over the ipsilateral motor cortex, was specific for inhibition of the LLSR. When the coil was moved anteriorly or to the midline, inhibition was significantly decreased. 7. We suggest that the inhibition of the LLSR of the long flexors of the fingers resulted from a reduction in excitability of the motor cortex produced by an inhibitory transcallosal pathway and conclude that the LLSR in this muscle has a transcortical component.

Electromyography↗
PubMed1995

Detection of movements imposed on human hip, knee, ankle and toe joints.

1. The angular displacements necessary for 70% correct detection were determined in normal subjects at the hip, knee and ankle joints, and the interphalangeal joint of the big toe. Angular velocities between 0.1 and 50 deg s-1 were tested. The hip and knee joints were tested in slight flexion and the ankle and toe joints were tested in the mid-range of the normal excursion. The joints were carefully supported for testing and the muscles acting at the joints were relaxed. 2. When detection thresholds and velocities were assessed in terms of angular displacements and angular velocities, proprioceptive performances at the hip, knee and ankle joints were superior to that at the toe joint. 3. When detection levels and displacement velocities were expressed in terms of linear displacements and velocities at the tip of the extended toe for all four joints, instead of in angular terms, the ankle gave the best performance and the hip and knee the worst. 4. The detection level and velocity data were expressed also in terms of proportional changes in the fascicle lengths of muscles operating these joints. Analysis in these terms showed that performance was similar at the hip, knee and ankle joints, but that performance for the toe was much poorer than for the other joints. 5. These results for the hip, knee and ankle are similar to those previously measured for the elbow and distal interphlangeal joint of the finger, and are consistent with the theory that muscle fascicle length is the variable of significance to the central nervous system. However, the proprioceptive performance at the big toe is notably poorer than all other joints studied and analysed in terms of this variable.

Adult↗
PubMed1995

The effect of voluntary contraction on cortico-cortical inhibition in human motor cortex.

1. It has been previously shown that in a relaxed target muscle, at short interstimulus intervals (ISIs) (up to 6 ms) a conditioning subthreshold transcranial magnetic stimulus can cause suppression of the EMG response evoked by a magnetic test stimulus. At longer ISIs (7-15 ms) facilitation of the test response is seen. This type of inhibition has been termed ipsilateral cortico-cortical inhibition. 2. The effect of a minimal tonic contraction on ipsilateral cortico-cortical inhibition has been investigated in the first dorsal interrosseous (FDI). 3. At short ISIs there was significantly less inhibition of the test response during the maintenance of minimal voluntary tonic contraction of the target muscle (FDI). 4. At longer ISIs (7-15 ms) there was significantly less facilitation of the test response during a tonic contraction than during relaxation. 5. Minimal activation of an ipsilateral proximal muscle (biceps) had no significant effect on the degree of inhibition seen in the relaxed target muscle (FDI). 6. We suggest that voluntary drive reduces the excitability of inhibitory circuits in cortical areas that project to the active muscle.

Adult↗
PubMed1995

Mapping of cortical sites where transcranial magnetic stimulation results in delay of voluntary movement.

Transcranial magnetic stimulation over the motor cortex has been shown to delay voluntary movement in man in a reaction time paradigm. In this study, we used a focal magnetic coil to stimulate 16 sites over the left hemisphere in 8 normal subjects. We measured the delay that occurred in the onset of a ballistic wrist flexion response and the size of the motor potentials evoked in the wrist flexors by stimulation at each site. The optimal site of stimulation to delay voluntary movement coincided with the optimal site to elicit an MEP in the agonist (flexor) muscle. However, MEPs were also obtained from some sites at which no delay in movement was induced.

Adult↗
PubMed1995

2',5'-oligoadenylate synthetase in interferon-alpha- and acyclovir-treated herpes simplex virus-infected cells.

The 2',5'-oligoadenylate (2-5A) synthetase pathway, induced by interferon-alpha (IFN-alpha), has been shown to be responsible for the antiviral action of IFN-alpha against some viruses. Studies were done to determine the role of this pathway in the anti-herpes simplex virus (HSV) action of IFN-alpha alone or in combination with acyclovir (ACV), a combination that leads to synergistic anti-HSV activity. Treatment of human corneal cells or Vero cells with 100 IU/ml of IFN-alpha induced expression of 2-5A synthetase mRNA and a 10-fold increase in 2-5A synthetase production compared with untreated cells. HSV infection alone did not induce 2-5A synthetase production, but when IFN-alpha-treated cells were infected with HSV, enzyme level was significantly increased (p < 0.05) compared with that in IFN-alpha-treated, uninfected cells. HSV infection actually decreased the level of 2-5A synthetase mRNA in IFN-alpha-treated cells. Although IFN-alpha treatment induced high levels of 2-5A synthetase with or without HSV infection, no activation of the latent endonuclease was detected by specific cleavage of ribosomal RNA. Treatment of infected cells with 5 microM ACV alone or combined with IFN-alpha did not increase 2-5A synthetase or endonuclease activities above those detected in cells not treated with ACV. The data indicate that the 2-5A synthetase pathway was inducible in corneal cells and Vero cells but did not appear to contribute to the anti-HSV activity of IFN-alpha alone or the synergistic activity of IFN-alpha combined with ACV.

2',5'-Oligoadenylate Synthetase↗
PubMed1995

On the mechanism of homologous synapsis in lycosid spiders.

Lycosid spiders have 13 pairs of telocentric chromosomes and 2 nonhomologous sex chromosomes in males. At leptotene, the kinetochore ends are attached to the nuclear envelope via thickened attachment plaques. Homologous synapsis begins at the attachment plaques and proceeds zipper-like through the length of the synaptonemal complex. We have tested whether or not this simple form of homologous synapsis is obligatory by inducing reciprocal translocations. Since we find many irradiated cells with quadrivalents at diakinesis-prometaphase and metaphase I, clearly a backup system exists that can bring together homologous segments disparate from each other in the nucleus. This mechanism apparently does not depend on end-initiated synapsis. Furthermore, we have found in previous studies that wolf spider bivalents are always unichiasmate, with either proximally or distally placed chiasmata. Since many chain quadrivalents, but no ring quadrivalents, were seen in this study, crossing over and chiasma placement obey a different set of rules when homologous segments are switched between chromosomes.

Animals↗
PubMed1995

Effect of interferon-alpha on the steady-state levels of thymine, thymidine, guanine, and guanosine metabolites in herpes simplex virus-type 1-infected cells.

Interferon-alpha (IFN-alpha) combined with acyclic guanine analogs synergistically inhibits replication of herpes simplex virus type 1. IFN-alpha treatment influenced the metabolism of exogenously supplied nucleobases and nucleosides in a manner expected to contribute to synergistic activity. IFN-alpha treatment of infected human cornea stromal cells or Vero cells significantly reduced steady-state levels of acid soluble metabolites of thymine, as well as thymidine, that accumulate early during virus replication but did not affect metabolism of thymine and thymidine in uninfected cells. IFN-alpha treatment significantly reduced the ability of uninfected cells to accumulate acid-soluble metabolites from guanine, but not guanosine. The effects of IFN-alpha on nucleobase/nucleoside metabolism could contribute to synergistic antiviral activity by reducing the accumulation of thymidine/thymine metabolites and decreasing the guanine taken into cells.

Acyclovir↗
PubMed1994

The effects of information load and speech rate on younger and older aircraft pilots' ability to execute simulated air-traffic controller instructions.

In this applied study of memory for orally presented information, 15 younger and 15 older pilots heard recorded air-traffic controller (ATC) messages in the context of six simulated flights. The ATC messages varied in length (3 vs 4 items), speech rate (235 vs 365 wpm), and type of command (course commands consisting of headings and altitudes vs radio/transponder commands consisting of radio frequencies and transponder codes). Older pilots made more execution errors on average and the age difference was greater for the radio/transponder commands, which contained more unique digits than the course commands. Although longer message lengths and faster speech rates led to higher error rates, the increases were not more marked in the older group. Backward digit span was correlated with communication performance, but the older group's lower level of accuracy was not explainable in terms of differences in digit span.

Adult↗
PubMed1994

Flight simulator performance of younger and older aircraft pilots: effects of age and alcohol.

OBJECTIVE: To determine if older pilots forgot more about a learned flight task after a 10-month delay than did younger pilots and if the anticipated greater skill loss led older pilots' performance to be more disrupted by alcohol. DESIGN: Repeated measures comparative group design examining the effects of alcohol versus placebo in two age groups (younger and older) and at two timepoints: acute intoxication, at a Blood Alcohol Concentration (BAC) of 0.10%, and 8 hours post-drink. SETTING: University medical center research laboratory. SUBJECTS: Fourteen younger (mean age = 27; SD = 4.21; range 21-34) and 13 older (mean age = 60; SD = 6.27; range 51-69) pilots, recruited from local flying clubs, with current FAA medical certificates. METHODS: We examined the effects of alcohol versus placebo in the two age groups and at two times, ie, acute intoxication (target BAC 0.10%) and 8-hour post-drink. Subjects flew a Frasca 141 simulator in a flight task that they had previously learned but not practiced for several months. After completing a baseline flight, pilots were tested during either an alcohol or a placebo condition at the two timepoints. The main outcome measure was a composite measure of flight performance based upon the mean of eight component standardized scores from different aspects of the flight task. RESULTS: We found detrimental effects of alcohol on the main outcome measure both at the acute and 8-hour post-drink testing. There was also no significant difference between the older and younger pilots' performance of the flight task or in susceptibility to alcohol either while intoxicated or during hangover. CONCLUSIONS: This study replicates the findings of earlier studies that an 8-hour waiting period from "Bottle-to-Throttle" is insufficient but finds little difference according to age in recollection of a previously learned task or in susceptibility to either acute or hangover effects of alcohol.

Adult↗
PubMed1994

Regulation of herpes simplex virus thymidine kinase in cells treated with a synergistic antiviral combination of alpha interferon and acyclovir.

Alpha interferon (IFN-alpha) and acyclovir (ACV) are synergistic in their anti-herpes simplex virus activities. IFN-alpha treatment reduced the herpes simplex virus thymidine kinase (TK) activity present in cells 6 h postinfection, while steady-state levels of TK mRNA remained at or above the amount in infected, untreated cells. The inhibition of TK production by IFN-alpha treatment appeared to be transient and translational, not transcriptional.

Acyclovir↗
PubMed1994

Serum antibody response to recombinant major inner capsid protein following human infection with group B rotavirus.

Recombinant major inner capsid protein (VP6) of the IDIR strain of group B rotavirus (GBR) was incorporated in a solid-phase immunoassay to access antibody response to infection in humans. Expression of VP6 in insect cells permitted design of a highly sensitive assay that avoided the contaminants present in GBR antigens obtained from fecal specimens. Among patients infected with the ADRV strain of GBR in China, increased reactivity with recombinant VP6 was observed in convalescent-phase sera in comparison with sera obtained shortly after infection (P = 0.0084). Anti-VP6 antibodies were detectable as soon as 7 days after onset of gastrointestinal symptoms, and serum reactivity persisted in specimens drawn more than 1 year after infection. Solid-phase immunoassay with recombinant VP6 was next employed in order to assess anti-GBR antibody in 513 serum specimens obtained from 423 Maryland residents (ages, 7 months to 96 years; median age, 42 years). Four individuals (< 1%) exhibited serum antibodies directed against the recombinant VP6 (ages, 54 to 95 years; mean age, 77 years). Examination of 129 additional serum specimens including some from other geographic regions of the United States failed to reveal the presence of anti-GBR antibody. Anti-GBR antibody was also not detected in any of 131 serum specimens from 60 staff and residents of a nursing home in Switzerland. While infection of humans with GBR has been uncommon in these locations outside of China, the detection of serum antibodies in older individuals in the United States either indicated an unknown, age-related risk factor or may have indicated infection in the more distant past. The availability of these reagents should allow surveys for GBR infection among additional populations that have not previously been investigated.

Adolescent↗
PubMed1994

Depression in secondary epilepsy: relation to lesion laterality.

Patients with epilepsy often have depressive disorders. This association may be particularly prominent in secondary epilepsy from a left hemisphere lesion. Among 1611 outpatients with epilepsy 272 patients were identified whose seizures originated from a structural brain lesion other than mesial temporal sclerosis. Sustained depressive disorders had occurred in 25 (9%) of these patients with secondary epilepsy. The depressed patients were compared with the remaining patients without depression with regard to location of lesion laterality and seizure variables. The only group difference was unilateral left hemisphere lesions in 58% of the patients with depression compared with only 21% of the non-depressed patients (chi 2 = 10.4, p = 0.006). This finding supports the idea of a relation of depression with epileptogenic lesions in the left hemisphere.

Adult↗
PubMed1994

Acute and 8-hour effects of alcohol (0.08% BAC) on younger and older pilots' simulator performance.

This preliminary study examined the acute and 8-hour effects of alcohol at a target peak BAC of 0.08% on pilot performance. Fourteen younger (mean age 27.6 years) and fourteen older (mean age 60.3 years) pilots flew a Frasca 141 simulator in a scenario that included ATC communications and emergencies. Plots were tested during an alcohol and placebo condition at three timepoints: predrink, acute intoxication, and 8 h postdrink. Of eight performance measures, two showed statistically significant effects related to alcohol. First, cockpit monitoring was poorer when pilots were intoxicated, with recovery at 8 h. Second, younger pilots made more communication errors under the influence and there was no significant recovery at 8 h. Older pilots made more communication errors than younger pilots, but possibly because of methodological problems, older pilots' communication performance was not significantly impaired by alcohol. These results provide direction for future research.

Adult↗