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Biomedical subjects

R A Ashley

Publications and source records attributed to R A Ashley.

At least 19 recordsLinked to original sources
PubMed2001

Effect of trap position, habitat, and height on the capture of pepper maggot flies (Diptera: Tephritidae).

Trapping results indicate that pepper maggot, Zonosemata electa (Say), flies occupy tree canopies adjacent to fields when not on host plants. Several in- and near-field trap positions were used to find a reliable monitoring system for adult pepper maggots. Traps baited with liquid ammonium hydroxide (Stills-style trap), hung in the canopy of trees on the edges of pepper fields, caught significantly more Z. electa flies than when positioned lower along the treeline or in the field. In a second experiment, significantly more pepper maggot flies were captured in sugar maples compared with choke cherry trees, which indicates a pest preference for certain nonhost habitats. The lowest trap height tested (2.1 m) failed to capture Z. electa flies in either tree species when the pest population level was low. These studies demonstrated that pepper maggot flies can be reliably detected with Stills-style traps positioned at approximately 6.4 m height within the canopy of sugar maple trees adjacent to pepper fields. Fruit oviposition scars also are useful site-specific indicators of pepper maggot presence/absence and may aid in determining if insecticide applications are necessary and in timing sprays.

Animals↗
PubMed1999

Clinical trials of a matrix metalloproteinase inhibitor in human periodontal disease. SDD Clinical Research Team.

After demonstration by Golub et al. of the ability of the tetracyclines to inhibit elevated collagenolytic activity in animal models of periodontal diseases, a clinical development program was initiated to demonstrate the potential of a subantimicrobial dose of doxycycline (SDD) to augment and maintain the improvements in clinical parameters of adult periodontitis (AP) afforded by conventional nonsurgical periodontal therapy. Clinical trials were carried out in which a number of different SDD dosing regimens and placebo were compared in patients administered a variety of adjunctive nonsurgical therapies. Measured parameters included levels of collagenase activity in gingival crevicular fluid (GCF) and gingival specimens, clinical attachment levels (cALv), probing pocket depths (PD), bleeding on probing (BOP), and subtraction radiographic measurements of alveolar bone height. When used as an adjunct to either scaling and root planing or supragingival scaling and dental prophylaxis, SDD was shown to reduce collagenase levels in both GCF and gingival biopsies, to augment and maintain cALv gains and PD reductions, to reduce BOP, and to prevent loss of alveolar bone height. These clinical responses arose in the absence of any significant effects on the subgingival microflora and without evidence of an increase in the incidence or severity of adverse reactions relative to the control groups. It is proposed that one of the mechanisms of action of SDD is as an inhibitor of pathologically elevated MMPs, including neutrophil and bone cell collagenases (MMP-8 and MMP-13), which are associated with the host response in chronic AP, and that SDD provides a novel systemic approach to the management of AP.

Adult↗
PubMed1998

How do tetracyclines work?

This paper is a summary of a panel discussion by the following panelists: L. Golub, J. te Koppele, G. Nieman, M. Nelson, R. Ashley, T. Sorsa, and S. Simon. The panel discussed the mechanisms by which the tetracyclines and their non-antimicrobial counterparts may provide therapeutic efficacy in a variety of chronic and acute diseases.

Adult↗
PubMed1991

Far-field recording of compound muscle action potentials produced during brachial plexus stimulation.

In 15 normal subjects, compound muscle action potentials (CMAPs) produced during electrical stimulation of the brachial plexus were obtained at a distance (far field) from their sources (upper-limb muscles). These far-field CMAPs were recorded at the forehead, neck, and tip of the middle finger and were referred to a relatively inactive region (contralateral forearm or knee). At the proximal recording site (neck or forehead), the far-field CMAPs were generally triphasic in appearance when all of the muscles of the upper limb were activated during brachial plexus stimulation. The initial component was a negative wave; this was followed by a positive component which terminated in a negative potential. At the distal recording site (tip of middle finger), the far-field CMAPs usually had a biphasic appearance, with an initial positivity followed by a period of negativity. The contours of the major components of the far-field CMAPs were frequently interrupted by a series of small amplitude negative and positive peaks or inflections.

Action Potentials↗
PubMed1991

Construction of an electrode for intraoperative nerve stimulation.

The electrode described in this paper consist of a barrel or handle with its conducting cable and a detachable stimulating tip. It is constructed of inexpensive and commercially available materials and is disposable. During the course of a stimulation study, electrode tips of different lengths or curvatures may be substituted without the need to replace the electrode barrel and cable.

Electric Stimulation↗
PubMed1990

Pathologic findings in brains of patients with focal epileptic seizures who had a craniotomy procedure.

This report reviews the pathologic findings in brains of 12 patients with focal epileptic seizures who had a craniotomy procedure. A majority of patients (seven) had either a cerebral neoplasm or a developmental abnormality (tuberous sclerosis and hamartoma), and these were found in six of the nine patients with chronic and intractable seizures. Four patients had cortical gliosis or scarring, and one had a bacterial brain abscess. Ten patients had a visible focal structural lesion during cranial imaging procedures, and in two instances, the MRI study was more sensitive than the CT in detecting a cerebral lesion.

Adolescent↗
PubMed1990

Volume-conducted or "far-field" compound action potentials originating from the intrinsic-hand muscles.

When a recording electrode is situated at a relatively far and roughly equal distance from multiple muscle action potential (MAP) sources such as the intrinsic-hand muscles (far-field recording), the individual MAPs generated by muscle fibers may contribute to the resultant compound potential with nearly equal weights depending on the orientation of the individual MAP fields. This is in contrast to recording MAPs directly over the muscle (near-field recording), in which the resultant potential primarily reflects the MAPs that were near the recording electrode. Far-field recorded compound MAPs(CMAPs) thus may provide another dimension or perspective into viewing the overall spatio-temporal relationship among MAPs generated by a large number of muscle fibers. In this study, we described CMAPs from intrinsic-hand muscles that were recorded at a distance from their potential sources.

Action Potentials↗
PubMed1989

Cortical somatosensory evoked potentials during acute hemorrhagic hypotension.

Cortical somatosensory evoked potential (SEP) recording to lower-limb stimulation was performed on a patient to monitor surgery for scoliosis. Intraoperatively, the patient developed acute and irreversible hemorrhagic hypotension. Cortical SEPs were clearly present with systolic blood pressures in the low 50s and upper 40s (mm Hg). The potentials deteriorated significantly with systolic pressures in the low 40s and disappeared with further reduction in systemic blood pressures.

Child↗
PubMed1989

Construction of a simple multi-lead electrode for intraoperative nerve recording. Technical note.

In the operating room, a fast and accurate means of recording nerve action potentials (NAP's) is always desirable. The multi-lead recording electrode described in this paper contains these desirable features. It can survey and obtain a number of NAP's from different nerve segments at the same time and under the same recording condition. The fixed distances between the recording leads enable quick calculation of conduction velocities of different nerve segments. Construction of the electrode is simple, and it can be designed to suit individual needs. The cost is marginal, reflecting primarily the costs of the original subdermal needle electrodes. The device is both safe and disposable.

Action Potentials↗
PubMed1989

Relationship between the location of the ground electrode and size of electrical stimulus artifacts.

In simulated electrophysiologic recordings, electrical stimuli were applied to the upper limbs of ten subjects. Then, stimulus artifacts were recorded using different ground locations, while all other technical parameters were kept constant. Stimulus artifacts were relatively large (often reaching a maximum amplitude) when stimulating electrodes were between ground and recording electrodes. Artifacts were relatively small (commonly arriving at a minimum and never at a maximum value) when recording electrodes were between ground and stimulus sites. When the ground was situated between stimulating and recording electrodes, the stimulus artifacts had about an even chance (40-50%) of achieving either a maximum or a minimum amplitude value. These findings do not seem to support the traditional belief that the best ground location to reduce the size of the stimulus artifacts is between points of stimulation and recording.

Electric Stimulation↗
PubMedDate not supplied

Transmission of acoustic or vibratory signals from a contracting muscle to relatively distant tissues.

In 20 normal subjects, acoustic or vibratory signals generated during sustained voluntary isometric contraction of the biceps brachii muscle were recorded directly over the muscle belly. The signals were also recorded simultaneously at a distance from the contracting biceps muscle over the posterior upper arm near the triceps muscle. Frequency amplitude spectra (FAS) of the recordings were determined. The amount of transmission of the most dominant vibratory signal from the biceps muscle to the posterior arm was estimated from the amplitude ratio of similar frequency peaks in the FAS obtained from recordings in these two separate regions. The mean amplitude ratio was 0.46. This finding suggests that when several groups of muscles are contracting simultaneously, there may be significant transmissions of acoustic signals from one muscle to the other. These transmissions could potentially interfere with the selective recording of sounds produced by a specific muscle.

Adult↗
PubMedDate not supplied

Effect of interelectrode recording distance on morphology of the antidromic sensory nerve action potentials at the finger.

In 15 normal subjects, antidromic median sensory compound nerve action potentials (SCNAPs) were recorded supramaximally from the middle finger with ring electrodes, using different interelectrode recording distances. The onset latencies were identical in all recording instances. The peak latency and amplitude of the major negative deflection continued to increase with increasing interelectrode distance. At and beyond a 4 cm interelectrode recording separation, they both achieved maximum values and did not increase further. On the other hand, the duration and area did continue to increase with increasing interelectrode separation. These findings suggest that in normal individuals, the true onset latency, peak latency, and amplitude are well reflected in the median SCNAP when it is recorded with an interelectrode distance of 4 cm or more at the finger; thus, they can easily be standardized. The SCNAP duration and area, however, are more variable since they both continue to change with increasing interelectrode recording separation without approaching a saturation value.

Action Potentials↗
PubMedDate not supplied

Relationship between the size of the recording electrodes and morphology of the compound muscle action potentials.

To determine the effect of recording electrode size on the compound muscle action potentials (CMAPs), maximally evoked CMAPs were obtained from the abductor digiti minimi muscle in ten normal subjects with circular-shaped surface recording electrodes of different diameters (4, 6, 8, 10, 12, and 14 mm). The electrodes were concentrically located on the same recording point on the muscle at its endplate zones when obtaining the CMAPs. The CMAP onset latency remained unchanged for all recording electrode sizes. The CMAP amplitude decreased with increasing electrode size. The mean absolute amplitude difference between CMAPs recorded with a 4-mm diameter electrode and those with a 14-mm diameter electrode was 1.22 mV, representing an amplitude decrement of 10% with this increase in electrode size. The general shape or morphology of the CMAPs was relatively well preserved.

Action Potentials↗