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Biomedical subjects

R W Beuerman

Publications and source records attributed to R W Beuerman.

107 records · Page 6Linked to original sources
PubMed1979

Corneal pain evoked by thermal stimulation.

The thermal sensitivity of the eyelid and cornea was compared using an automated apparatus to produce stimulus pulses of known magnitude and duration over the range 33--45 degrees C. Subjects reported only temperature sensation when the skin of the upper eyelid was tested; however, corneal stimulation in the same subjects was always perceived as nociceptive. The possibility that other ocular tissues may be involved in the pain responses was shown to be unlikely by direct experimentation or by calculation of heat flow in those tissues. Cornea and eyelid thresholds were compared in relationship to the structural and physical properties of these tissues. It was found that the nerve endings of the corneal epithelium are less sensitive to temperature change when compared to the thermal receptors of the eyelid. It is concluded that the cornea is useful for the experimental study of pain.

Adult↗
PubMed1978

Comparative clinical assessment of corneal sensation with a new aesthesiometer.

A new version of an aesthesiometer offers particular advantages such as portability without risk of damage to the filament, easy filament replacement, and an expanded stimulus range. We compared the performance of this new instrument to that of the Cochet-Bonnet aesthesiometer in a clinical setting on herpetic patients. Using both instruments, we obtained paired measurements on the normal and diseased corneas from five test loci placed over the corneal surface. Statistical analysis of the normalized data showed that the data obtained by the new instrument were similar to those of the Cochet-Bonnet aesthesiometer.

Cornea↗
PubMed1975

Slow potentials of the turtle olfactory bulb in response to odor stimulation of the nose.

Odor stimulation of the nose in the box turtle and the gopher tortoise produced a characteristic series of slow potentials in the olfactory bulb which were referred to as the odor evoked response. When recorded with direct coupling, the odor evoked response had 3 components: wave I, a short duration monophasic event; wave II, a long duration variation in the DC potential; and wave III, an oscillatory potential superimposed on wave II. Waves I and II were negative at bulbar surfaces receiving olfactory input and positive deep within the bulb. This series of potentials could be evoked by 3 methods of odor stimulation: (1) large puffs delivered from odorant test bottles, (2) small puffs delivered from a syringe and (3) continuous flow with concentration and nasal flow rate parameters controlled by an olfactometer. When the odor evoked response was recorded at a bulbar locus, these potentials were seen in response to each stimulation and the amplitudes of each wave were reproducible with the same stimulus. The amplitudes of the 3 waves were compared in the gopher tortoise and differed with the 3 odorants tested--high purity geraniol, technical grade geraniol and amyl acetate. Odorant concentration also directly affected the response amplitudes of all 3 wave components. The amplitudes of waves I and III markedly decreased with closely spaced stimulations recovering to near the initial values when the interstimulus interval was increased severalfold. This series of sensory evoked potentials is considered to reflect the processing of odor information from the olfactory receptors by the olfactory bulb.

Anesthetics↗
PubMed1975

Graphic-digitizer analysis of axon spectra in ethmoidal and lingual branches of the trigeminal nerve.

Sections were removed from the lingual and ethmoidal nerves of cats and histologically prepared, and the fibers were analyzed under the light microscope. Neural dimensions were measured by a new technique, employing a graphic digitizer and computer. The outline of a neural structure was traced with the digitizer pen, and the total number of axons, their cross-sectional areas, shapes, diameter spectra, and locations within the nerve were calculated. Both nerves had unimodal axon spectra with the peak between 2 and 6 mum diameter. Differences in axon composition occurred over the diameter range of 9 to 20 mum; the lingual nerve had many axons in this range, the ethmoidal nerve only a few. The total number of myelinated axons was near 4000 in the lingual nerve, near 1400 in the ethmoidal nerve; only the latter had many large-sized Remak bundles (containing C-fibers). Most myelinated axons were not perfectly circular but exhibited various degrees of distortion.

Analog-Digital Conversion↗
PubMedDate not supplied

Confocal microscopy of corneal penetration by tarantula hairs.

In vivo identification of foreign bodies in the cornea may be impossible if the size and/or location precludes visualization by slit lamp biomicroscopy, which has an upper limit of magnification of 50x. These limitations became obvious when we attempted to identify the offending material in the inflamed eye of a patient who complained of foreign body sensation after contact with a pet tarantula. As a model of this clinical situation, we used a newly developed tandem scanning confocal microscope to observe and to photograph tarantula hairs as they penetrated the corneal stroma and endothelium and entered the anterior chamber in rabbit eyes. We found that, experimentally, the hairs penetrated the ocular tissues apparently without inciting inflammation or causing fibrosis. The instrument we used--a prototype with a Nipkow disk from Noran, Inc. (Middleton, Wis.) and a 25/0.8 na glycerin immersion lens (Plan-Neofluor, Zeiss)--provides magnifications of 100-500x, real-time viewing in vivo, optical sectioning, contrast control, high resolution, processing through image analysis systems, and video and hard copy output. We believe that confocal microscopy offers a new approach to the identification and localization of foreign bodies in the anterior segment, as well as to the visualization and diagnosis of ocular diseases, including bacterial, fungal, and other parasitic invasions, in the human eye.

Animals↗
PubMedDate not supplied

Tumor necrosis factor-alpha and interleukin-1 induce activation of MAP kinase and SAP kinase in human neuroma fibroblasts.

Two cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1), which are released by macrophages during the early inflammatory phase of nerve injury, are known to induce activation of mitogen-activated protein kinase (MAPK) and stress-activated protein kinase (SAPK), which locate at different signal transduction pathways and are involved in cell cycle G0/G1 transition and cellular proliferation in human fibroblasts. Activation of these two protein kinases by the cytokines may stimulate fibroblast proliferation in damaged nerves and thereby play a role in the formation of a neuroma, a disorganized mass of tissue that interferes with neural regeneration and repair. To investigate the possibility that this mechanism is operative in neuroma formation, we used cultured, serum-starved fibroblasts from surgically removed human neuromas stimulated with TNF-alpha and/or IL-1 alpha and IL-1 beta, and measured the activation of MAPK and SAPK using myelin basic protein (MBP) and human c-Jun (1-169) glutathione S-agarose transferase (GST) fusion protein as substrates. For comparison, neuroma fibroblast cultures were also stimulated with phorbol 12-myristate 13-acetate (PMA) and platelet-derived growth factor-AB (PDGF-AB), a potent activator for MAPK. TNF-alpha and both forms of IL-1 produced a rapid activation of MAPK, with a peak at 15 min for TNF-alpha stimulation, and a peak at 30 min for IL-1 stimulation. TNF-alpha combined with either IL-1 alpha or IL-1 beta produced a synergistic effect on the activation of MAPK. The increases in MAPK induced by TNF-alpha and IL-1 were similar to the increases induced by PMA and PDGF-AB. To confirm the presence of MAPK, immunoprecipitation and immunoblotting were carried out on experimental and control lysates. TNF-alpha and IL-1 also increased activation of SAPK, but to a lesser extent than MAPK. PMA and PDGF-AB were also much less effective in stimulating activation of SAPK. Our findings indicate that TNF-alpha and IL-1 activate parallel signal transduction pathways in human neuroma fibroblasts, and that they are relatively stronger activators of MAPK than of SAPK. Previous studies have convincingly demonstrated that MAPK and SAPK are involved in human fibroblast proliferation. The results of our study suggest that TNF-alpha and IL-1 may play a role in frustrating functional nerve regeneration after injury by stimulating these two kinases, which, in turn, leads to fibroblast proliferation and formation of neuromas.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMedDate not supplied

Proteomic analysis of human tears: defensin expression after ocular surface surgery.

Human tear protein profiles were monitored by surface enhanced laser desorption/ionization-time-of-flight mass spectrometry ProteinChip technology (SELDI-TOF ProteinChip) and liquid chromatography-mass spectrometry (LC-MS). Tears were collected from 21 patients scheduled for surgery to remove an ocular surface neoplasm prior to surgery (day 0) and on days 1, 3, and 30 postoperatively. Using this proteomic approach, we verified that three human alpha-defensins (HNP-1, HNP-2, and HNP-3) were significantly up-regulated in their expression after surgery and that their levels decreased to approximately normal by day 30 by which time healing was complete. Further confirmation of the identity of the alpha-defensins in human tears was made by LC purification, trypsin digestion, and ESI-MS/MS analysis of their tryptic digests. The concentrations of HNP-1 and HNP-2 were determined and shown to be markedly increased after ocular surface surgery. The results of the study suggest that human alpha-defensins HNP-1, HNP-2, and HNP-3 are up-regulated after surgery, and may in addition to their antimicrobial properties have an important role in wound healing.

Amino Acid Sequence↗
PubMedDate not supplied

Comparison of corneal epithelial wound healing after photorefractive and lamellar keratectomy.

BACKGROUND: The rate of corneal epithelial wound healing may be determined, in part, by the characteristics of the stromal surface. The excimer laser has the ability to produce a highly uniform ablated surface, which may facilitate reepithelialization after photorefractive keratectomy (PRK). METHODS: The rate of corneal epithelial wound healing after excimer laser PRK was compared with the rate of reepithelialization after manual lamellar keratectomy. Ten rabbits received a 4-mm diameter ablation in one eye (fluence = 160 mJ/cm2) and a shallow, 5-mm diameter, manual lamellar keratectomy in the contralateral eye. At 0, 4, 8, 12, 24, 36, 48, 60, and 72 hours after wounding, sodium fluorescein was instilled, and photographs were taken, converted to video images, and digitized. Wound area was calculated for each time point and converted to wound radius; the slopes of the wound radius, plotted over time, were compared to determine rates of healing. Scanning electron microscopy was performed immediately after wounding to examine surface regularity. RESULTS: By 24 hours after wounding, corneas that had undergone PRK demonstrated a significantly faster rate of epithelial wound healing compared with eyes that underwent lamellar keratectomy (33.4 +/- 1.9 microns/hr vs 27.8 +/- 1.4 microns/hr, respectively, for 12 to 72 hours) (p < 0.0001). Scanning electron microscopy showed greater stromal surface irregularity in the corneas that had undergone lamellar keratectomy, compared with the laser-ablated corneas. CONCLUSIONS: This study demonstrates that the rate of epithelial wound healing is significantly faster after excimer laser PRK than after lamellar keratectomy in the rabbit. Variations in surface regularity and wound edge profile may contribute to differences in wound healing.

Animals↗
PubMedDate not supplied

Diclofenac sodium attenuates neural activity after photorefractive keratectomy in rabbits.

BACKGROUND: Photorefractive keratectomy for treating myopia has been associated with severe postoperative pain. The purpose of the present study was to investigate, in a rabbit model, the early effects of laser ablation on the physiology of the sensory nerves of the cornea. METHODS: Neurophysiologic monitoring of the corneal nerves was carried out 4 to 6 hours after 5-mm diameter, circular PRK ablations with a central depth of 85 microns. The effect of topical 0.1%, 0.25%, and 0.5% diclofenac sodium on the physiologic response to chemical and mechanical stimulation was evaluated. Corneas were prepared for anatomic studies of corneal innervation. RESULTS: Heightened neural activity was observed in the corneal nerves after ablation, and exaggerated responses to sensory stimulation with hypertonic sodium chloride solutions were recorded. Diclofenac sodium at 0.1% decreased the response to 0.5 M NaCl and 0.7 M NaCl to 67 +/- 9% and 68 +/- 7% (mean +/- standard error) of the control response. Mechanically sensitive nerves were more resistant to diclofenac; 0.1% diclofenac had no effect, but 0.25% diclofenac reduced the response significantly (P < 0.05). Anatomic observations showed that the ablation extended through the neural plexus. By 72 hours, long neurites tipped with growth cones had advanced into the injured region, indicating the initiation of neural regeneration. CONCLUSIONS: Diclofenac sodium was effective in attenuating neural activity in the cornea after excimer laser ablation. The action of this agent was shown to be different from that of a topical anesthetic, which rapidly and totally inhibited the response to all forms of stimulation.

Animals↗
PubMedDate not supplied

[Comparative study of tears protein composition in patients after photorefractive keratectomy and laser specialized keratomileusis].

Changes in the protein spectrum of the lacrimal fluid, resultant from refraction ocular surgery (photorefraction keratectomy, PRK, and laser specialized keratomileusis, LASIK) were evaluated. Lacrimal fluid was collected before operation and in various terms after it in 28 patients (48 eyes) subjected to PRK and in 34 patients (59 eyes) subjected to LASIK. Biochemical analysis of the lacrimal fluid was performed on a mass spectrometer. After PRK the greatest changes in the protein spectrum occurred immediately after the operation before reepithelialization. Changes after LASIK were negligible. Refraction laser operations cause changes in the protein composition of tears, LASIK being more physiological than PRK from viewpoint of intactness of the protein composition of tears.

Biomarkers↗
PubMedDate not supplied

Real-time confocal microscopy of keratocyte activity in wound healing after cryoablation in rabbit corneas.

A modified tandem scanning confocal microscope was used for real-time in vivo examination of the rabbit cornea following a cryogenic injury. The corneas of New Zealand white rabbits were frozen with a probe that had been cooled by immersion in liquid nitrogen, effectively destroying keratocytes in a central 5 mm diameter zone throughout the total thickness of the cornea. In these eyes, keratocyte repopulation and corneal stromal wound healing proceeded similarly to that which occurs after epikeratophakia, a refractive surgical procedure designed to change the curvature and optical power of the cornea. In epikeratophakia, a cryolathed donor corneal stroma lenticule is sutured onto the bare stroma of the recipient cornea. The collagen tissue lenticule is repopulated by keratocytes (corneal fibroblasts) that migrate in from the host cornea. In our study, the confocal microscope permitted sequential, noninvasive examination of the corneal stroma in the treated animals. Necrosis of the keratocytes, followed by activation of the remaining viable cells in the corneal periphery, was observed in the first 2 to 3 days after cryo injury. A fine stromal fibrous network was seen to develop; in three eyes, this network progressed to the development of a retrocorneal fibrous membrane and dense stromal fibrosis, both of which resulted in significant loss of corneal clarity. Our results suggest that the confocal microscope may be a valuable tool to provide much needed information on wound healing processes at the cellular level after corneal surgery and injury.

Animals↗
PubMedDate not supplied

Analysis of rabbit tear fluid using capillary electrophoresis with UV or laser-induced fluorescence detection.

In preliminary studies of the development of tear analysis methodology that may eventually be useful in the clinical setting, the authors evaluated various protocols for analyzing rabbit tears by capillary zone electrophoresis (CZE). Conditions included the use of a 50-mM monosodium phosphate buffer, pH 2.5, or a 400-mM sodium borate buffer, pH 8.9, both with ultraviolet (UV) detection, as well as a 50-mM borate buffer, pH 8.5, with laser-induced fluorescence (LIF) detection of ATTO-TAG CBQ (Molecular Probes, Inc., Eugene, OR, U.S.A.) derivatized tears. All CZE analyses were performed with a P/ACE System 2100 instrument equipped with System Gold software (Beckman Instruments, Fullerton, CA, U.S.A.), using a 50 microns x 57 cm (50 cm to the window) fused-silica capillary, at 25 degrees C, with constant voltage of 20 kV for UV detection and 11 kV for LIF detection. Tear samples were collected from normal rabbit eyes by means of 10-microL glass micropipets. The volume of each sample was approximately 2 microL. Analysis using the phosphate buffer with UV detection produced as many as 35 peaks in each sample, of which 11 peaks were readily discerned. This compared favorably with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, which produced 32 bands with silver staining and 11 quantifiable bands with Coomassie brilliant blue staining. Many of the tear protein components have yet to be identified. CZE analysis with the high-ionic-strength borate buffer with UV detection produced only four peaks, and the low-ionic-strength borate buffer with LIF detection produced only six peaks. CZE analysis was completed in less than 1 hr, compared with 7-8 hr for SDS-PAGE. In summary, CZE analysis of tear fluid is comparable to CZE analysis of other bodily fluids and shows great potential for use in clinical diagnosis as well as for enhancing our understanding of the cellular actions of tears on the front of the eye.

Animals↗