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Biomedical subjects

M G Davidson

Publications and source records attributed to M G Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1992

Enzyme-linked immunosorbent assays for the detection of Toxoplasma gondii-specific antibodies and antigens in the aqueous humor of cats.

Serum and aqueous humor samples, collected from 14 clinically normal cats and 96 cats with clinical evidence of intraocular inflammation, were assayed with ELISA for Toxoplasma gondii-specific immunoglobulin M (IgM), T gondii-specific IgG, T gondii-specific antigens, total IgG, and total IgM. Additionally, serum was assayed with ELISA for feline leukemia virus p27 antigen and antibodies against the feline immunodeficiency virus as well as with an immunofluorescent antibody assay for antibodies against feline coronaviruses. Calculation of the Goldmann-Witmer coefficient (C-value) for the T gondii-specific antibodies detected in aqueous humor established the likelihood of local antibody production. Serologic evidence of present or prior infection by an infectious agent was found in 81.9% of the clinically affected cats from which serologic results were available (77/94 cats). Seropositive results for toxoplasmosis were found in 74.0% of the clinically affected cats. Anterior segment inflammation was found in 93.1% (81/87 cats from which information was available) of the clinically affected cats, most of which were older males. Toxoplasma gondii-specific antibodies were not detected in the aqueous humor of 6 seropositive, clinically normal cats. The C-values for aqueous T gondii antibodies were greater than 1 in 44.8% of the cats and greater than 8 in 24.0% of the cats. Response to treatment with clindamycin HCl was positive in 15/20 (75%) of the T gondii-seropositive, clinically affected cats treated with this drug. In 13/15 (86.7%) T gondii-seropositive, clinically affected cats having a C-value greater than 1, response to treatment with clindamycin HCl was positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Lens-induced uveitis in dogs: 151 cases (1985-1990).

During a 5-year period, phacolytic uveitis was diagnosed in 202 eyes of 151 dogs admitted to the veterinary teaching hospital. The diagnosis of phacolytic uveitis was based on the finding of a cataractous lens and anterior uveitis, unassociated with other identifiable causes of uveal inflammation. The most commonly affected breeds were the Toy and Miniature Poodle (35%) and the American Cocker Spaniel (19%). The mean age was 7.0 years for all breeds, 5.1 years for the Cocker Spaniel, and 9.0 years for the Poodle breeds. Evidence of cataract resorption was visible in 72% of the eyes. Fifty-one dogs were affected bilaterally and 100 dogs unilaterally. The mean interval between recognition of the cataract and the onset of lens-induced uveitis (LIU) was 17 months; mean times of 25 and 11 months were seen in the Poodle breeds and American Cocker Spaniel, respectively. The mean age of dogs requiring greater than 1 revisit before the inflammation had subsided was 5.5 years. Complications, referable to the uveitis, were seen in 14% of eyes, the most important of which were glaucoma (16 eyes) and phthisis bulbi (9 eyes). Lens extraction surgery was done on 50 LIU-affected eyes, and on 35 normal eyes in LIU-affected animals. The 2- and 6-month success rates for LIU-affected eyes were 78 and 39%, respectively, and for normal eyes in LIU-affected animals were 85 and 71%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1992

Thiamin deficiency in a colony of cats.

Twenty-eight cats belonging to a cat rescue society developed clinical signs consistent with thiamin deficiency after being fed a proprietary canned food containing inadequate amounts of the vitamin. Five of the cats died but the others recovered after appropriate therapy. The diagnosis was based on clinical signs, histopathological findings, food analysis and response to treatment.

Animal Feed↗
PubMed1992

Job stress and burnout in acute and nonacute pediatric nurses.

OBJECTIVE: To identify predictors of burnout in pediatric nurses and to compare the incidence of burnout, job stress, anxiety and perceived social support in acute and nonacute care pediatric nurses. DESIGN: Prospective correlational-descriptive methodology was used to predict high, moderate or low burnout from length of work experience, perceived work stress and social support and anxiety. SUBJECTS AND SETTING: Registered nurses (n = 121) employed full-time in neonatal and pediatric intensive care units and pediatric intermediate care units. MEASUREMENTS AND RESULTS: Measures of job stress, anxiety, experience, social support and burnout were compared in acute and nonacute care pediatric nurses. The overall mean incidence of burnout was in a moderate range for both acute and nonacute care pediatric nurses for the emotional exhaustion and depersonalization subscales and in the high range of personal accomplishment subscales of the Maslach Burnout Inventory. Analysis of variance revealed no differences between groups. However, when nurses were grouped by high, moderate and low burnout scores, chi-square analysis revealed significant differences. More acute care nurses reported high burnout and more nonacute care nurses reported low burnout. Discriminant function analysis revealed that job stress was the strongest significant predictor of burnout, followed by state anxiety, coworker support, trait anxiety and experience on the unit. CONCLUSIONS: Even though high burnout levels are more frequent in acute care pediatric nurses, burnout is a problem in both acute and nonacute care pediatric nurses. The pattern of results suggests that efforts directed toward reducing anxiety and job stress and increasing coworker support, particularly for less experienced nurses, might reduce burnout.

Adult↗
PubMed1991

Clinical evaluation of 1% cyclosporine for topical treatment of keratoconjunctivitis sicca in dogs.

Keratoconjunctivitis sicca (KCS) is a prevalent and often vision-threatening condition in dogs. In several reports, 2% cyclosporine (cyclosporin A, CsA) was described as effective in modulating the clinical signs of KCS. This study was designed to compare the efficacy of 1% CsA vs a placebo, using a randomized double-blind clinical trial. Topical administration of 1% CsA significantly improved Schirmer wetting values and subjective markers of corneal health as compared with the placebo. In the dogs treated with topical administration of 1% CsA, the clinical signs of KCS were improved in 81.8% of cases.

Administration, Topical↗
PubMed1991

Acute blindness associated with intracranial tumors in dogs and cats: eight cases (1984-1989).

Rostral and middle cranial fossa tumors affecting the optic chiasm and resulting in acute visual deficits were diagnosed in 7 dogs and 1 cat. Blindness and dilated nonresponsive pupils were the primary signs in all animals. Other concurrent neurologic deficits were either absent or were equivocal. Behavioral changes, including signs of depression and lethargy, were noticed in 1 dog and the cat subsequent to the onset of blindness. Retinal function was assessed as normal by electroretinography in all animals. The histologic necropsy diagnosis was pituitary carcinoma in 1 dog and the cat and paranasal sinus carcinoma with intracranial extension in 1 dog. A cytologic diagnosis of polycentric lymphosarcoma affecting the optic chiasm was diagnosed in 1 dog. In the remaining 4 dogs, results of computed tomographic imaging or endocrine function testing suggested pituitary gland neoplasia. Four dogs were treated with cobalt-60 radiation or chemotherapy. There was partial return of visual function in only 1 of the dogs treated with radiation.

Acute Disease↗
PubMed1991

Amino acid substitutions at tryptophan-51 of cytochrome c peroxidase: effects on coordination, species preference for cytochrome c, and electron transfer.

Amino acid replacements of an aromatic residue, Trp-51, which is in contact with the heme of yeast cytochrome c peroxidase have a number of significant effects on the kinetics and coordination state of the enzyme. Six mutants at this site (W51F, W51M, W51T, W51C, W51A, and W51G) were examined. Optical and EPR spectra show that each of these mutations introduces a shift from the 5-coordinate to 6-coordinate form, and slightly increases the asymmetry of the heme ligand field. Conversion from a 6-coordinate high-spin form at pH 5 to a 6-coordinate low-spin form at pH 7 is observed for several of the variants (W51F, W51T, and W51A), while W51G and W51C appear as predominantly low-spin species between pH 5 and 7. Addition of 50% glycerol prevents the facile conversion to the low-spin conformation for W51F, W51T, and W51A, and only W51F can be stabilized in a 5-coordinate configuration by glycerol. For the oxidation of cytochrome c by H2O2, three of the variants (W51F, W51M, and W51T) exhibit values of kcat(app) that are greater than for the wild-type enzyme, while the other mutations give decreased rates of enzyme turnover. Unlike the wild-type enzyme, which functions more efficiently with cytochrome c from yeast than with the horse heart protein, the mutant W51F does not show a preference for substrate from its native organism. The three mutants which exhibit increased values of kcat(app) show a pH optimum at 6.8 compared with that of 5.25 for the wild-type enzyme when measured with horse heart cytochrome c. This shift in pH optimum is not observed with yeast cytochrome c. Construction of single and multiple mutations at Trp-51, Ile-53, and Gly-152 shows that these kinetic properties are not due to natural amino acid variations observed at these sites. Pre-steady-state kinetics show that the bimolecular rate constant for the fast phase of the reaction of the enzyme with H2O2 is only slightly decreased from 3.03 (0.09) X 10(7) to 2.2 (0.1) X 10(7) M-1 s-1 for W51F and to 1.5 (0.1) X 10(7) M-1 s-1 for W51A. The slow phase of the reaction (4.9 s-1) which contributes approximately 30% to the amplitude of the change for the wild-type enzyme is not observed for W51F or W51A.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1991

Efficacy of chloramphenicol, enrofloxacin, and tetracycline for treatment of experimental Rocky Mountain spotted fever in dogs.

Dogs were experimentally inoculated with Rickettsia rickettsii to characterize the comparative efficacies of chloramphenicol, enrofloxacin, and tetracycline for the treatment of Rocky Mountain spotted fever (RMSF). All three antibiotics were equally effective in abrogating the clinical, hematologic, and vascular indicators of rickettsial infection. Antibiotic treatment for 24 h was sufficient to decrease the rickettsemia to levels below detection by Vero cell culture. Early treatment with all three antibiotics resulted in a similar decrease in antibody titer, but acute and convalescent serum samples taken at appropriate times would have still facilitated an accurate diagnosis of RMSF in all but one dog, which did not seroconvert. We conclude that chloramphenicol, enrofloxacin, and tetracycline are equally efficacious for treating experimental canine RMSF.

Animals↗
PubMed1991

Burnout, job stress, anxiety, and perceived social support in neonatal nurses.

Forty-nine nurses working in neonatal intensive care were surveyed by using measures of job stress, burnout, anxiety, and perceived social support. On the Maslach Burnout Inventory, they scored in a moderate range of burnout for emotional exhaustion and depersonalization and in a high range of burnout for sense of personal accomplishment. Stepwise regression analyses revealed that higher job stress scores, higher anxiety scores, perception of less supervisor (head nurse) support, and less experience were associated with higher burnout subscale scores.

Adult↗
PubMed1990

Treatment of glaucoma by use of transscleral neodymium:yttrium aluminum garnet laser cyclocoagulation in dogs.

Neodymium:yttrium aluminum garnet (Nd:YAG) laser energy was transsclerally applied to the ciliary body of 56 eyes of 37 dogs for treatment of glaucoma. Forty-four eyes were glucomatous at the time of treatment, and 12 normotensive eyes with ciliary cleft closure were treated prophylactically. Glaucoma was primary in 35 dogs and secondary in 2 dogs (1 eye in each dog). Energy was delivered by a general surgical Nd:YAG laser via a hand-held, 600-muc-diameter flexible quartz fiber. The mean (+/- SD) number of spots treated per eye was 35 (+/- 9.7), with mean energy per burst of 7.1 (+/- 2.6) J; mean total energy delivered to the eyes was 228 (+/- 81) J. Follow-up evaluation was available for 42 eyes from 2 to 4 weeks after treatment, and for 32 eyes from 12 to 24 weeks after treatment. Treatment success, defined as maintenance of intraocular pressure less than 25 mm of Hg, was achieved in 83% (20/24) of glaucomatous eyes evaluated between 12 and 24 weeks of treatment. Of 4 treatment failures, 3 were eyes devoid of uveal pigment. The consistent acute effects of treatment were conjunctival vascular congestion and blood-aqueous barrier disruption, recognized clinically by the presence of aqueous flare. Hyphema developed in 16% (9/56) of eyes; hyphema resolved without complication in all but 2 eyes. A common long-term complication of treatment was cataract formation, recognized in 37% (12/32) of eyes evaluated at 12 to 24 weeks. Cataracts were sufficiently dense to obstruct vision in 4 eyes. Phthisis bulbi was observed in 1 eye.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Lymphocyte population changes in cats naturally infected with feline immunodeficiency virus.

Feline immunodeficiency virus (FIV) is associated with feline acquired immunodeficiency syndrome (FAIDS) and has been suggested as a model for HIV-induced human AIDS. The most obvious immunological defect in HIV infection is a reduction in CD4+ cell numbers and an inversion of the CD4:CD8 ratio. To determine whether the same is true in FIV infection, we analyzed by flow cytometry using a panel of monoclonal antibodies to feline lymphocyte populations the CD4:CD8 ratios in cats naturally infected with the virus. We report that 13 of 19 FIV-infected cats had ratios below the 5th percentile of normal cats (0.57, established from analysis of 39 normal cats) and 18 of 19 had ratios below 1. Repeated analyses over a period of several months revealed the inverted ratios to be consistent. Analysis of lymphocyte numbers in FIV-infected cats shows that the inverted ratios are due to a decrease in CD4+ T cells, while CD8+ T and B cells remain relatively normal in number. Analysis of a group of cats with a variety of other chronic diseases, including feline leukemia virus (FeLV) infections, revealed a near-normal distribution of CD4:CD8 ratios. These findings are similar to those in HIV infections and indicate that, like HIV, FIV causes a selective reduction in CD4+ cells and should be an excellent model for studying retrovirus-induced AIDS.

Animals↗
PubMed1990

The causes of glaucoma in cats.

The cause of glaucoma in 131 enucleated eyes from 128 cats was determined in a retrospective histologic study. Obliteration of the ciliary cleft by diffuse iridal melanoma (38 eyes), or other neoplasms (14 eyes), or by the presence of idiopathic lymphocytic-plasmacytic anterior uveitis (53 eyes) were the most frequent lesions likely to explain the development of glaucoma. Secondary changes of inner retinal atrophy, optic disc cupping, scleral thinning with megaglobus, and atrophy of ciliary processes were similar to those described in dogs and human beings with chronic glaucoma. In light of the duration and severity of the glaucoma, the degree of inner retinal atrophy was often less than expected. Diffuse corneal edema and breaks in Descemet's membrane, changes typical of glaucoma in other species, were rarely detected. Eyes with chronic uveitis and glaucoma had collapsed ciliary clefts, iridoscleral adhesions, and posterior displacement of the iris. We were unable to determine whether these changes were consequences of the uveitis and thus responsible for the development of glaucoma, or if they were merely the result of the chronic glaucoma itself.

Animals↗
PubMed1990

Vascular permeability and coagulation during Rickettsia rickettsii infection in dogs.

The vascular permeability of the ocular fundus, alterations in the coagulation system, and plasma concentrations of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were studied in dogs following intradermal inoculation with 5 x 10(5) TCID50 of Rickettsia rickettsii. Twenty-four to 48 hours after the onset of fever and rickettsemia, multifocal areas of retinal vasculitis were evident, which corresponded to areas of altered vascular permeability demonstrated by fluorescein angiography. The number and intensity of retinal vessels with sodium fluorescein leakage peaked during the second week after inoculation, and retinal vascular permeability remained altered during the third week of infection, well past the phase of clinical and clinicopathologic recovery. Development of retinal vasculitic foci was associated with thrombocytopenia, increased concentrations of circulating fibrinogen, and slight prolongation of activated partial thromboplastin time. Increased concentrations of fibrin/fibrinogen degradation products were detected in 4 of 9 dogs. Despite the degree of vascular endothelial damage evident on fluorescein angiographic and histologic studies in these dogs, plasma TXB2 and 6-keto-PGF1 alpha concentrations were not increased.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Kinetics of IgM and IgG responses to experimental and naturally acquired Rickettsia rickettsii infection in dogs.

The kinetics of specific IgM and IgG antibody response was characterized in four 9-month-old Beagles after inoculation of 2 x 10(2) plaque-forming units (PFU) of Sheila Smith strain of Rickettsia rickettsii. Immunoglobulin M antibodies were first detected by indirect immunofluorescence on postinoculation (PI) day 9, peaked by PI day 20, and were no longer detectable by PI day 80. Immunoglobulin G antibodies became detectable between PI days 22 and 28, peaked by PI day 42, and decreased gradually through PI day 130. Subsequent challenges with R rickettsii on PI days 216 (2 x 10(2) PFU/dog) and 1,029 (5 x 10(4) tissue culture infective dose [TCID50]/dog) resulted in slightly different serologic responses. The initial challenge exposure failed to increase the concentration of IgG antibodies and induced only low concentrations of IgM antibodies. After the second challenge inoculation, IgM antibodies were not detectable and the concentration IgG antibodies increased slightly. Clinical abnormalities and seroconversion were documented in control dogs following each challenge exposure. Examination of acute and convalescent serum samples from 55 dogs in which Rocky Mountain spotted fever was suspected clinically suggested that sole evaluation of IgM antibodies in acute-phase serum would result in inaccurate diagnoses because of false-positive and -negative results. Use of a composite conjugate that detects IgM and IgG antibodies to R rickettsii appears to be satisfactory for diagnostic purposes; however, concurrent quantitation of IgM antibodies may facilitate serodiagnosis in a select group of dogs in which a four-fold increase in convalescent antibody titer is not detected by use of the composite conjugate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Ocular manifestations of Rocky Mountain spotted fever in dogs.

Dogs were examined ophthalmoscopically to determine the prevalence and type of ocular lesions associated with naturally acquired Rocky Mountain spotted fever (RMSF). In a consecutive series of 11 dogs with serologically confirmed RMSF, 9 had ocular involvement reflecting various degrees of vascular damage, including subconjunctival hemorrhage, hyphema, anterior uveitis, iris stromal hemorrhage, retinal petechiae, and focal areas of retinal edema and perivascular inflammatory cell infiltrate. The ophthalmic lesions generally were mild, and most resolved without complication after systemic administration of appropriate antibiotics. The high prevalence of ocular lesions in these dogs suggested that critical ophthalmologic evaluation is a useful diagnostic tool for the early detection and management of RMSF in dogs.

Animals↗
PubMed1989

Experimental ocular herpesvirus infection in the cat. Sites of virus replication, clinical features and effects of corticosteroid administration.

Experimentally induced ocular feline herpesvirus 1 (FHV-1) infection was studied in 30 specific pathogen-free cats. In ten cats, the ability of five field isolates of FHV-1 to replicate in the epithelium and substantia propria of cornea and conjunctiva was demonstrated by histochemical techniques. Feline herpesvirus 1 was found to preferentially infect and induce necrosis of conjunctival epithelium. Although significant histologic lesions were not induced, all FHV-1 strains were observed to replicate in corneal epithelium; minimal viral antigen was detected in the corneal stroma. The course and clinical features of ocular FHV-1 infection were then studied over a period of 60 days in two groups of ten cats: in one group, infection was preceded by administration of subconjunctival betamethasone. In each of these groups, a distinct clinical syndrome developed. In cats not receiving corticosteroids, a course of epithelial keratitis, characterized by the formation of punctate and dendritic epithelial lesions, persisted for up to 24 days postinfection. In the corticosteroid treated group, a chronic (greater than 60 days) stromal keratitis developed, characterized by geographic epithelial ulceration, interstitial edema and deep vascularization. Other complications observed in corticosteroid-treated animals included decreased tear production, calcific-band keratopathy and a unique stromal disorder of cats termed corneal sequestration. The results of this study indicate that while epithelial keratitis may occur during primary infection, stromal keratitis does not, unless immune responsiveness to FHV-1 is concomitantly suppressed. This feature is similar to naturally occurring HSV-1 keratitis of humans, but contrasts to other animal model systems in which stromal keratitis predictably occurs during primary infection. Study of this animal model, therefore, may allow unique insights into the events preceding the establishment of stromal keratitis.

Animals↗