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Biomedical subjects

M G Davidson

Publications and source records attributed to M G Davidson.

67 records · Page 4Linked to original sources
PubMed1989

In vitro susceptibility of feline herpesvirus-1 to vidarabine, idoxuridine, trifluridine, acyclovir, or bromovinyldeoxyuridine.

In vitro activities of 9-[( 2-hydroxyethoxy] methyl) guanine (acyclovir), (E)-5-(2-bromovinyl)-2'deoxyuridine, 9-beta-D-arabinofuranosyladenine (vidarabine), 5-iodo-2'-deoxyuridine (idoxuridine), and 5-trifluoromethyl-2'-deoxyuridine (trifluridine) were studied against 6 strains of feline herpesvirus-1. A significant difference was not detected among viral strains in their susceptibility to these compounds (P = 0.442). The relative potency of these compounds was trifluridine much greater than idoxuridine greater than vidarabine greater than bromovinyldeoxyuridine much greater than acyclovir. Concentrations of trifluridine and idoxuridine (0.67 and 6.8 microM, respectively) required to reduce plaque numbers by 50%, compared with that of controls, were significantly lower (P less than 0.001) than were those of other compounds.

Acyclovir↗
PubMed1988

Use of methyl methacrylate orbital prostheses in dogs and cats: 78 cases (1980-1986).

To prevent cosmetically undesirable orbital concavity after enucleation, methyl methacrylate spheres were implanted into the orbits of 73 dogs and 5 cats. In all cases, follow-up reports were obtained until suture removal 2 weeks after surgery, and for 58 animals (79%) until 6 months after surgery. Information was available for 46 animals (60%) 1 year after surgery, 28 animals (36%) 2 years after surgery, and 7 animals (9%) 3 years after surgery. Implants failed in 3 dogs and 2 cats. Complications were not detected in the remaining 73 animals (93%), and owners were pleased with the cosmetic results. The causes of implant failure in dogs varied; however, in cats, fluid accumulation was the consistent complication associated with failure. Orbital implantation of methyl methacrylate spheres was found to be a safe, practical, and inexpensive method of improving the cosmetic appearance of dogs requiring enucleation. Although the number of cats evaluated was limited, the accumulation of orbital fluid in a high percentage of those suggested that orbital implants may be less successful in this species.

Animals↗
PubMed1988

Neodymium:yttrium, aluminum, and garnet laser energy delivered transsclerally to the ciliary body of dogs.

Using a hand-held optical fiber, a surgical neodymium:yttrium, aluminum, and garnet laser was used transsclerally on the left ciliary body of 25 dogs. Dogs were assigned to groups and were given low (100 J) and high (238 J) energy levels. In 12 dogs given 100-J energy, the intraocular pressure decreased a mean value of 6 mm of Hg below that in the untreated right eye. However, intraocular pressure returned to the pretreatment value 1 week after treatment. Intraocular lesions were not found by histologic examination 28 days later. In the second group of 13 dogs treated with 238-J energy, 6 were euthanatized 7 days after treatment and 7 were euthanatized 28 days after treatment. A mean decrease in intraocular pressure of 10 mm of Hg in the treated left eye, relative to the untreated right eye, persisted throughout the evaluation period. In eyes examined histologically 7 days after treatment, ciliary hemorrhage and necrosis were prominent. Other histologic changes were minimal and consisted principally of iris stromal hemorrhage. Of 7 dogs examined for 28 days after treatment, 6 remained sighted; in 1 dog, extensive intraocular hemorrhage occurred, eventually resulting in phthisis bulbi. Ciliary atrophy and fibrosis were the important histologic lesions observed 28 days after treatment. Laser energy delivered transsclerally by this optical system effectively induced ciliary necrosis and may be an effective treatment for canine glaucoma.

Animals↗
PubMedDate not supplied

Success rates of unilateral vs. bilateral cataract extraction in dogs.

Postoperative results of 113 unilateral and 77 bilateral extracapsular cataract extractions (EC-CEs) in dogs were evaluated retrospectively. Restoration or improvement of functional vision was achieved in 79.6% of the eyes in dogs with unilateral extraction and 85.7% of the eyes in dogs with bilateral extractions at weeks 4 to 6. Complications occurring 6 weeks to 9 months after lens extraction lessened the surgical success rate in both groups. Twenty-six percent of the dogs in which bilateral lens removal was performed suffered complications resulting in surgical failure in one eye. When using the criterion that one or both treated eyes had functional vision, a short-term success rate of 98.7% was found for bilateral extractions.

Animals↗
PubMedDate not supplied

Respiratory depressant and skeletal muscle relaxant effects of low-dose pancuronium bromide in spontaneously breathing, isoflurane-anesthetized dogs.

OBJECTIVE: To assess and compare the respiratory depressant and skeletal muscle relaxant effects of two low doses of a nondepolarizing neuromuscular blocker, pancuronium bromide. To determine if a "low dose" of pancuronium bromide can produce selective skeletal muscle relaxation in extraocular muscles sufficient to perform intraocular surgery while sparing or minimizing depression of muscles of ventilation. STUDY DESIGN: Blinded, randomized crossover, placebo controlled study. ANIMALS: Six healthy, adult mongrel dogs weighing 20.8 +/- 1.9 kg. METHODS: Spontaneously breathing, isoflurane-anesthetized dogs received 0.02 mg/kg pancuronium bromide, intravenously (i.v.), (high dose [HD]), 0.01 mg/kg pancuronium bromide, i.v., (low dose [LD]), or saline placebo i.v. in a blinded, randomized crossover study. Indices of patient ventilation including tidal volume (Vt), respiratory rate (RR), and minute ventilation (VE) were recorded throughout the study period. Serial arterial blood gas analyses were performed at timed intervals. Neuromuscular blockade of skeletal muscle was assessed at timed intervals with train-of-four stimulus/response ratios. Eye position scores, based on the degree of ocular rotation from a neutral gaze axis, were assigned by an ophthalmologist who was blinded to the treatment given. RESULTS: VT and VE in HD dogs decreased by 82% from baseline after administration of pancuronium bromide. Similarly, Vt and VE in LD dogs decreased 40% and 55%, respectively. Decreased ventilation in HD dogs corresponded with significant (P< .05) neuromuscular blockade, as indicated by train-of-four ratio less than 75% between 0 and 60 minutes. Eye position scores in HD and LD dogs were suitable for intraocular surgery between 0 and 60 minutes. Eye position scores in five of six control dogs were unsuitable for intraocular surgery at any time period. CONCLUSIONS: LD dogs experienced only transient, mild to moderate respiratory depression compared with HD dogs, which experienced prolonged, moderate to severe respiratory depression. Both LD and HD dogs acquired and maintained eye position scores suitable for intraocular surgery between 0 to 60 minutes. A "low dose" of pancuronium bromide, which would provide adequate extraocular muscle relaxation while minimizing ventilatory depression, was not identified. CLINICAL RELEVANCE: All patients receiving any dose of neuromuscular blocking agents should be closely monitored and receive ventilatory assistance as needed.

Anesthesia, Inhalation↗
PubMedDate not supplied

Thoracic radiographic findings in dogs infected with Rickettsia rickettsii.

Sixteen beagle dogs were injected intradermally with Rickettsia rickettsii. The dogs were divided into four groups (n = 4): 1) infected, non-treated control; 2) infected, treated with doxycycline; 3) infected, treated with doxycycline and an anti-inflammatory dose of corticosteroid; and 4) infected, treated with doxycycline and an immunosuppressive dose of corticosteroid. Thoracic radiographs were made and ocular fluorescein angiography was performed on days 6, 10, 17 post-inoculation. A mild interstitial lung opacity was noted in 4/16 dogs on day 6, 5/16 on day 10 and 3/16 on day 17 post-inoculation. Increased retinal vascular permeability was noted in 8/16 dogs on day 6, 3/16 on day 10 and 1/16 on day 17 post-inoculation. Correlation between the presence of radiographic and retinal lesions was not significant (p = 0.08). Eleven, naturally infected, dogs with thoracic radiographs and a final diagnosis of RMSF were also evaluated. Four of the 11 dogs had an unstructured interstitial pattern. Dogs with acute, experimentally-infected or naturally-occurring RMSF may have subtle pulmonary changes characterized by an unstructured interstitial pattern.

Animals↗
PubMedDate not supplied

The intracapsular extraction of displaced lenses in dogs: a retrospective study of 57 cases (1984-1990).

Records of 48 dogs (57 eyes) that underwent intracapsular lens extraction (ICLE) of displaced lenses were reviewed. Preoperatively, 73% (19/26 eyes) of eyes with anterior luxations had secondary glaucoma compared to 43% (10/23 eyes) with subluxations and 38% (3/8 eyes) with posterior luxations. Forty-one of 57 eyes (72%) had vision and intraocular pressure (IOP) less than 30 mm Hg four to six weeks after surgery. This percentage declined to 61% (22/36 eyes) in three months and 53% (8/15 eyes) in 12 months. Eyes with glaucoma before ICLE had a lower success rate (66%) than eyes without (82%). Since secondary glaucoma was the most common cause of failure, this study suggests that removal of a subluxated lens or a posteriorly luxated lens should be recommended before the lens moves into the anterior chamber.

Animals↗
PubMedDate not supplied

Identification of rickettsiae in cutaneous biopsy specimens from dogs with experimental Rocky Mountain spotted fever.

Direct immunofluorescence reaction for Rickettsia rickettsii was performed on formalin-fixed, paraffin-embedded cutaneous biopsy specimens collected from dogs with experimental Rocky Mountain spotted fever (RMSF). A technique of trypsin digestion of deparaffinized, rehydrated sections was successful in demonstrating discrete, immunofluorescent organisms in endothelia and adjacent vessel walls in the dermis. R rickettsii was identified only in grossly evident dermal lesions (macular rash or oral vesicles) and was not apparent in randomly collected biopsy specimens from clinically normal inguinal skin. These results suggest that clinical application of this technique for diagnosis of RMSF may be limited in dogs without cutaneous lesions.

Animals↗