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Biomedical subjects

R B Davis

Publications and source records attributed to R B Davis.

233 records · Page 13Linked to original sources
PubMedDate not supplied

Enzyme-linked immunosorbent assay for detection of antibody to avian encephalomyelitis virus in chickens.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to avian encephalomyelitis virus (AEV) has been developed for determining whether existing AEV control programs adequately protect breeder hens. A partially purified AEV antigen was bound to microcuvettes for reaction with specific primary antibody. A second antibody, rabbit anti-chicken immunoglobulin G (IgG) conjugated with horseradish peroxidase, was employed to react with bound primary IgG. The relative amount of bound primary IgG was detected using ortho-phenylenediamine as a substrate for enzymatic production of a chromogen by horseradish peroxidase. Intensity of absorbance of the chromogen at 490 nm was related to the bound primary antibody by the titration method. Negative antisera were surveyed to establish an appropriate positive/negative cutoff level at twice the mean absorbance of negative sera at a 1:100 dilution. The test reagents for the ELISA were optimized by reagent titrations utilizing known positive and negative antisera for discrimination. The optimized ELISA had a coefficient of variation of from 1.2 to 3.3 for within-assay titer and of 2.4 for between-assay mean titer. Even though the ELISA detected only specific IgG, it was as accurate as the virus-neutralization test for evaluating the immune status of hens to AEV. Moreover, the ELISA was more economical in the use of reagents, time, and personnel and was free from dependence on susceptible embryos. Since ELISAs can be standardized and measured with manual or automated instruments, the derived ELISA can be easily and economically used to evaluate the immune status of breeder hens in commercial poultry operations.

Animals↗
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Infectious coryza: preventing complicated coryza with Haemophilus gallinarum and Mycoplasma gallisepticum bacterins.

Three types of infectious coryza were produced in unvaccinated chickens by challenge inoculums containing different combinations of Haemophilus gallinarum (HG) and Mycoplasma gallisepticum (MG). Monovalent and combination bacterins of HG and MG were tested to determine their efficacy against chronic complicated infectious coryza. Challenge exposure of vaccinates with MG and HG showed protection against the HG component to be immunotype-specific. Some protection against complicated coryza resulted from HG bacterins only, whereas MG bacterin was ineffective. Protection against transient and chronic coryza was provided by a combination MG-HG bacterin. Two doses of this bacterin gave better protection against upper respiratory clinical signs and lowered the incidence of airsacculitis.

Animals↗
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Mycoplasma challenge studies in budgerigars (Melopsittacus undulatus) and chickens.

An upper respiratory condition that resulted in 20% mortality in a flock of yellow-naped Amazon parrots was apparently caused by a concomitant infection of mycoplasmas and bacteria. Mycoplasma gallisepticum (MG), M. iowae, and an unidentified mycoplasma were isolated from the affected parrots. Budgerigars were experimentally infected with a parrot strain of MG designated MG(P) 1669 as well as with the R strain of MG and the F10-2 strain of M. synoviae (MS). Air-sac lesions were evident in all groups of challenged budgerigars, and MS and MG were cultured from the tracheas, air sacs, and lungs of the budgerigars up to 5 weeks postexposure. Serological findings were ambiguous and therefore considered unreliable. White leghorn and commercial broiler chickens challenged with the MG(P) 1669 isolate did not exhibit any significant air-sac lesions relative to the controls. However, MG was cultured from both groups of experimentally infected birds. Eight weeks after exposure, the white leghorns were seropositive to all MG antigens used in the agglutination test.

Air Sacs↗
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A viral disease of fledgling budgerigars.

Fledgling budgerigars from aviaries in Georgia and Texas were reported to have high rates of mortality. Affected birds died acutely and exhibited abdominal distention and reddening of the skin. Postmortem lesions were hydropericardium, enlarged heart and liver with areas of necrosis, and swollen, congested kidneys. Histologic examination of a variety of tissues revealed cells with enlarged nuclei containing inclusions. Electron micrographs revealed the presence of viral particles 42 to 49 nm in diameter in the nuclei of epithelial cells of the renal tubule.

Animals↗
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Characterization of a papovavirus isolated from fledgling budgerigars.

A virus suspected of causing high death rates in fledgling budgerigars in Georgia and Texas aviaries was isolated in budgerigar embryo fibroblasts inoculated with tissue homogenates from affected birds. Virus was most easily recovered from tissues containing many intranuclear inclusion bodies. Cytopathic effect on fibroblasts of all four isolates was characterized by a swollen nucleus followed by rounding and detachment of the affected cell from the monolayer. Properties suggesting the B-931 isolate belongs to the papovaviridae family are (1) presence of DNA; (2) insensitivity to treatment with CHCl3; and (3) presence of cubic viral particles 42 to 49 nm in diameter in the nucleus of infected chicken embryo fibroblasts. The isolate did not hemagglutinate erythrocytes of chickens, turkeys, budgerigars, guinea pigs, or type O humans and was basically stable against heating and freeze-thawing. An examination of fledgling budgerigars from infected aviaries demonstrated that sick birds carried more virus than healthy birds.

Animals↗
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Effects of selective dorsal rhizotomy on gait in children with cerebral palsy.

We wished to examine the effects of selective dorsal rhizotomy (SDR) on the gait patterns of children with cerebral palsy (CP). Nineteen ambulatory children underwent preoperative and 1-year postoperative gait analyses that included clinical assessment of joint range of motion (ROM) and muscle tone, three-dimensional motion analysis, and dynamic electromyography (EMG). The children were divided into two groups: independent ambulators (n = 11) and dependent ambulators (requiring a walking aid) (n = 8). Improvements in joint passive ROM and a reduction in lower extremity spasticity were noted. In both groups, positive pre- to postoperative improvements were noted in sagittal plane hip, knee, and ankle motion and there was a greater incidence of a plantar-grade foot position in stance. There was no change in the coronal plane motion of the pelvis and hip. A mean increase in anterior pelvic tilt for the independent ambulators was the only major negative change observed in this study. We conclude that SDR improves specific gait parameters in children with CP.

Ankle Joint↗
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Development of a knowledge-based electronic patient record.

To help clinicians care for patients with HIV infection, we developed an interactive knowledge-based electronic patient record that integrates rule-based decision support and full-text information retrieval with an online patient record. This highly interactive clinical workstation now allows the clinicians at a large primary care practice (30,000 ambulatory visits per year) to use online information resources and fully electronic patient records during all patient encounters. The resulting practice database is continually updated with outcome data on a cohort of 700 patients with HIV infection. As a byproduct of this integrated system, we have developed improved statistical methods to measure the effects of electronic alerts and reminders.

Acquired Immunodeficiency Syndrome↗
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Experimental coryza in broiler chickens. I. Effects of vaccination with Haemophilus gallinarum bacterin and its components on weight gains and resistance to infection.

Effects of a Haemophilus gallinarum bacterin and its components were studied in young broiler chickens. When the bacterin was administered subcutaneously in the dorsal neck region at 2 weeks of age, no significant differences in weight gains of vaccinated and control birds were detected at eight weeks of age. In four groups vaccinated at 1, 2, 3, or 4 weeks of age and challenged with virulent haemophilus organisms 3 weeks later, the incidence of clinical signs was 30% in the vaccinates and 60% in controls. The bacterin was equally protective at the four ages of administration. Caseous plugs were found at the vaccination sites in all birds which had received adjuvant either alone or in the complete bacterin. Signs of depression lasting about 24 hours were observed in the youngest birds injected with the bacterin, but overall weight gains were normal.

Animals↗
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Further observations on the use of a bivalent bacterin against Haemophilus gallinarum.

Chickens vaccinated with two doses of a bivalent Haemophilus gallinarum bacterin were protected against seven strains of the organism. Vaccinated and unvaccinated birds with antibody to Mycoplasma gallisepticum had increased HI titers when challenged with H. gallinarum. Birds positive for antibody to Mycoplasma gallisepticum which were not challenged showed no increase in HI titer.

Animals↗
PubMedDate not supplied

Effect of hamstring and psoas lengthening on pelvic tilt in patients with spastic diplegic cerebral palsy.

The purpose of this study was to evaluate the effects of hamstring lengthenings and psoas recessions over the brim of the pelvis (OTB) on pelvic function in the gait of patients with spastic cerebral palsy. Seventy-three patients were divided into four groups based on surgical intervention: medial hamstrings (n = 37), medial and lateral hamstrings (n = 12), medial hamstrings with psoas OTB (n = 9), and medial and lateral hamstrings with psoas OTB (n = 15). Three-dimensional gait analysis was completed both before and approximately 1 year after surgery. When pelvic position in gait was normal or posterior of normal preoperatively, there was a significant increase in pelvic tilt (p < 0.05) when medial and lateral hamstrings were lengthened, irrespective of simultaneous psoas OTB surgery. Medial hamstrings alone, with or without simultaneous psoas OTB, did not result in a significant change in pelvic position, irrespective of preoperative pelvic position. The only surgical combination that caused a reduction in excessive preoperative anterior pelvic tilt was medial and lateral hamstrings with psoas OTB, a 4 degrees change of limited clinical significance. In general, psoas and medial hamstring surgery have minimal effect on the pelvic position during gait. Medial and lateral hamstring lengthening will increase pelvic tilt if preoperative pelvic position is normal or slightly posteriorly tilted. The results of this study suggest that the fundamental determinants of pelvic position during gait postoperatively are the extent of hamstring surgery (medial only vs. both medial and lateral hamstring lengthening) and the preoperative position of the pelvis.

Cerebral Palsy↗
PubMedDate not supplied

The effects of ankle-foot orthoses on the ankle and knee in persons with myelomeningocele: an evaluation using three-dimensional gait analysis.

The purpose of this study was to determine the effects of the ankle-foot orthosis (AFO) on gait patterns in patients with low-level myelomeningocele and to identify any abnormal gait patterns that may lead to future knee instability and pain. A total of 28 children (26 L4-level sides, 18 L5-level sides, and 10 S1-2-level sides) underwent a three-dimensional gait analysis when ambulating barefoot and with AFOs. Results show significant improvements in sagittal plane function with reductions in excessive ankle dorsiflexion, increases in peak plantar flexor moment, and reductions in crouch and knee extensor moment in the L4 and L5 groups. The only improvement in the S1-2 group was a reduction in excessive dorsiflexion, but there was a reduction in power generation at the ankle. The S1-2 group had normal transverse plane knee motion in stance during barefoot walking that increased significantly (p < 0.01) with the AFO. Both the L5 and L4 groups showed greater-than-normal transverse plane knee motion in stance during barefoot walking that also increased significantly (p < 0.01) with the AFO. The results suggest that excessive knee transverse plane rotation may contribute to knee instability more than coronal plane abnormalities. The AFO in S1-2-level patients may be more detrimental for the knee than barefoot walking.

Ankle Joint↗