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Biomedical subjects

R D Montgomery

Publications and source records attributed to R D Montgomery.

At least 91 records · Page 5Linked to original sources
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The reharvested central third of the patellar tendon. A histologic and biomechanical analysis.

We assessed the histologic, mechanical, and structural properties of the reharvested central-third patellar tendon in greyhounds. Twelve dogs had the central third of the patellar tendon (5 mm) removed with corresponding bone blocks from the patella and tibia; the remaining tendon defect was loosely closed. Six dogs were sacrificed at 6 months and six at 12 months, and the central third of the patellar tendon was harvested from both the operative and the contralateral control knees. Analysis of the structural changes in the tendons revealed a significant increase in thickness for reharvested tendons at both 6 and 12 months when compared with controls. The entire residual tendons were narrower at 6 months and were shorter at 12 months compared with controls. Mechanical testing showed that the average failure load, ultimate tensile strength, strain at failure, and average modulus for the reharvested central third of the patellar tendon were significantly less than that of controls at both 6 and 12 months. Analysis of collagen fiber size by electron microscopy revealed a significant increase in collagen fiber diameter at 6 months (135 +/- 41 nm versus 49 +/- 4 nm) but no difference between the operative limbs and controls at 12 months. The reharvested bone-patellar tendon-bone complex does not have the same properties as the primary patellar tendon graft up to 1 year after harvest in a canine model, and its use for revision cruciate ligament reconstruction must be carefully reexamined.

Animals↗
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Winner of the AlbertTrillat Young Investigator Award. The effects of aggressive notchplasty on the normal knee in dogs.

We assessed the possible association between an aggressive intercondylar notchplasty and histopathologic, radiographic, and gait changes to the knee. Three groups of six adult greyhounds were observed for 6 months. Group I dogs had a sham operation. Group II dogs had a 4-mm notchplasty of the lateral femoral condyle where it articulates with the lateral tibial spine. Group III dogs had a 7- to 8-mm notchplasty of the lateral femoral condyle to simulate the long-term effects of an overly aggressive notchplasty. Force plate gait analyses were not significantly different for any dogs at 3 and 6 months. Histopathologic studies (hematoxylin and eosin and safranin O stains) revealed notchplasty area remodeling with a thin layer of lamellar bone covered by fibrous connective tissue. Both Group II and III dogs had significant loss of lateral femoral condyle and trochlear groove articular surface proteoglycans. The radiographic notch width index remained unchanged throughout the study for Group I; the indexes increased immediately after surgery in Groups II and III because of the notchplasty, but after 6 months these values returned to near-preoperative measurements. An aggressive intercondylar notchplasty caused articular cartilage histopathologic changes at 6 months consistent with those found in knees with early degenerative arthritis. Significant refilling of a non-impinged notchplasty occurred by 6 months after surgery. Our results raise concern about the effects of aggressive intercondylar notch widening in humans.

Analysis of Variance↗
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A retrospective study of canine hip dysplasia in 116 military working dogs. Part I: Angle measurements and orthopedic foundation for animals (OFA) grading.

The progression of hip dysplasia was investigated in 116 military working dogs. Serial pelvic radiographs were graded for degree of dysplasia and degenerative joint disease (DJD). Norberg angles, angles of inclination, and joint space widths were measured. There was a significant correlation between the Norberg angle and the degree of dysplasia (p less than 0.0001). Angles of inclination and joint space width measurements did not demonstrate a correlation to canine hip dysplasia. Dysplastic dogs had a significant estimated risk for development of DJD compared to normal dogs (p less than 0.0001; odds ratio of 70.2). Dogs with normal hip conformation at 24 months of age or older did not develop moderate nor severe DJD.

Animals↗
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A retrospective study of canine hip dysplasia in 116 military working dogs. Part II: Clinical signs and performance data.

The progression of hip dysplasia was investigated in 116 military working dogs. Medical records were reviewed for any clinical history of hind-limb lameness. Pelvic radiographs were studied for evidence and degree of hip dysplasia, degenerative joint disease, or both. The number of months each dog worked was determined. Each dog's age at termination from service and cause of death (or euthanasia) were recorded. The mean months of work for normal and dysplastic dogs were evaluated using the Student's t-test. No significant difference was found in the total number of months worked between normal and dysplastic dogs (p greater than 0.05).

Animals↗
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Consequences to chicks hatched from Escherichia coli-inoculated embryos.

An Escherichia coli causing negligible mortality in embryonated chicken eggs was adapted to grow in media containing nalidixic acid. This isolate (EcNAL) was inoculated into 12-day-old embryonated eggs. Additional embryos inoculated with tryptose phosphate broth (TPB) served as controls. Six days later, all surviving eggs were moved to hatching units. One hatcher contained half of the TPB-inoculated eggs; the chicks hatching from these eggs served as negative controls. The EcNAL-inoculated eggs and the remaining TPB-inoculated eggs were moved to a second hatcher and allowed to hatch together; chicks hatching from these TPB-inoculated eggs served as contact controls. On day of hatch and at intervals thereafter, chicks from each of the treatment groups were sampled. Their body and yolk weights were recorded, and various tissues were cultured for the presence of the EcNAL bacterium. Hatchability of the EcNAL-inoculated embryos was markedly lower than that of either control group. Chicks from EcNAL-inoculated embryos also had low but detectable levels of mortality, lowered body weights, and increased yolk-to-body weight ratios. These same chicks had persistently high levels of EcNAL in the yolk and lower but detectable levels of the organism in the lungs and tracheas, which lasted a few days. The contact controls, on the other hand, were similar to the negative controls as far as having negligible mortality, steadily increasing body weights, and declining yolk-to-body weight ratios. However, in contrast to the negative controls, EcNAL was recovered primarily from the respiratory tract of the contact controls for a brief period of 3-4 days after hatch.

Animals↗
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A comparison of the gland of Harder response and head-associated lymphoid tissue (HALT) morphology in chickens and turkeys.

The immunofunctional response of the gland of Harder (GH) was compared in chickens and turkeys using an in vivo assay previously developed for use in chickens. The GH were surgically removed (GHx) from leghorn chicks at 1 day of age and from poults at 2 days of age. Intact birds of each species served as controls. During the fourth week of age, both GH-intact and GHx chicks were exposed to killed Brucella abortus antigen by the ocular or intraperitoneal route. One week later, serum and tears were collected and assayed for antibodies to B. abortus. In addition, all birds were killed at the end of the trial period, and the heads were fixed and processed for histologic examination. Various components of the head-associated lymphoid tissue (HALT) including the GH, nasal glands, lacrimal glands, lacrimal ducts, eyelid conjunctiva, and nasal cavity mucosa/submucosa, were evaluated microscopically using a scoring system to estimate quantity and degree of development of immune tissue in those sites. Results of all analyses indicate that functional response and morphology of the HALT are comparable in turkeys and chickens.

Animals↗
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An inexpensive system to monitor air flow in isolation units.

Isolation units are used extensively for conducting infectious disease research in poultry. By necessity, these units are airtight and receive air only through electrically powered ventilation systems. Therefore, interruptions in electrical service to these units present a serious hazard to the animals they contain. A system was designed to monitor the air flow through isolation units and to alert animal caretakers in the event of any interruption in air flow. The "intelligence" of the system relies on an electronic monitor connected to a telephone line that places alerting telephone calls when it detects loss of air flow to the units. The system is constructed from easily acquired and relatively inexpensive parts and components.

Animals↗
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Effects of an Arkansas strain of infectious bronchitis vaccine on the head-associated lymphoid tissue (HALT).

Chicks were vaccinated with an Arkansas strain of infectious bronchitis virus (IBV) vaccine when they were 1 day (Trial 1) or 4 weeks old (Trial 2). Starting at 4 weeks 3 days of age, chicks in both trials were subjected to an assay that measures the immunofunctional response of the gland of Harder (GH), one of the components of the head-associated lymphoid tissue (HALT). The assay involved multiple ocular exposures to killed Brucella abortus antigen, after which tears were collected and titered for antibodies to B. abortus. Following this, select tissues from vaccinated and unvaccinated chicks were collected and examined microscopically for specific lesions. Both functional and structural alterations were detected in the HALT of IBV-vaccinated chicks. Antibody titers to B. abortus in vaccinated chicks were significantly lower (P less than 0.05) than in unvaccinated controls. Structurally, there were elevations (P less than 0.01) in the number of lymphoid cells and follicles found in the mucosal lining of the nasal cavity. This occurred in the vaccinated chicks of both trials. Otherwise, histologic changes were confined to the chicks vaccinated at 4 weeks of age (Trial 2). In that trial, there were elevations in lymphoid-cell and follicle numbers in the eyelid (P less than 0.01) and lacrimal gland (P less than 0.05).

Analysis of Variance↗
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Influence of antigen concentration, inoculation interval, number of exposures, type of housing, and placement concentration on the tear antibody response to Brucella abortus in chickens.

A series of trials was run in leghorn chicks to examine select conditions affecting the tear antibody response to killed Brucella abortus antigen given by eyedrop administration. Specific conditions examined were concentration of antigen, number of antigen exposures, and interval between antigen exposures. Trials were also run to determine the earliest age at which the assay was functional in both broilers and leghorns. Two types of housing (isolators and battery cages) were examined, as were two levels of placement concentration, or bird density (0.32 and 0.64 ft. [0.03 and 0.06 m2]/chicken). All trials included intraperitoneally inoculated chicks as a comparison; tears as well as serum were assayed for antibodies. Of the various antigen regimens evaluated, two exposures of 20% B. abortus given 3 days apart was found to give a satisfactory antibody response in the tears 1 week later. Furthermore, response to B. abortus was found to be somewhat proportional to age, with the minimum age for a satisfactory response being 3 weeks in leghorns or 4 weeks in broilers. Statistically, there were no differences in antibody responses due to the types of housing or levels of placement used.

Age Factors↗
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Effect of infectious bursal disease virus vaccines on persistence and pathogenicity of modified live reovirus vaccines in chickens.

Two commercially available live reovirus vaccines, alone or in combination with two infectious bursal disease virus (IBDV) vaccines, were evaluated for safety and efficacy in specific-pathogen-free leghorn chicks. Four trials were conducted to evaluate the vaccine combinations. At periodic intervals during the trials, tissues were collected and assayed for residual reovirus and examined for histological changes. Six weeks following reovirus vaccination, all treatment groups were challenged with a virulent field isolate of reovirus and sampled 1 week later for the final time. The two reovirus vaccines were safe and effective if given at 1 week of age, regardless of whether the vaccinates had been exposed to IBDV at 1 day. However, both reovirus vaccines persisted in the tendons of 1-day-old vaccinates. The effects of IBDV vaccines were generally minor and reflected by increases in the number of pre-challenge or post-challenge virus recoveries from some of the treatment groups receiving both type vaccines.

Animals↗
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The effect of Harderian adenectomy on the antibody response in chickens.

Intact chicks and those that had their glands of Harder (GH) removed (GHx) at 1 day of age were studied for their response to optically or intraperitoneally (IP) applied antigens. Following exposure of the chicks to sheep red blood cells (SRBCs), killed Brucella abortus, or bovine serum albumin (BSA), serum and tear samples were collected and assayed for antibodies. Of the two sources of antibodies, the serum generally had higher levels than did the tears. The only exception to this occurred in the intact chicks inoculated by the eye, in which serum and tear levels were equivalent. With SRBCs, no difference could be detected between the two routes of inoculation. However, IP inoculation produced higher levels of antibody in the serum of intact and GHx chicks inoculated with B. abortus or BSA and in the tears of the GHx chicks exposed to B. abortus. Removal of the GH resulted in a consistent decrease in antibody levels in the tears, regardless of the route of exposure. Although this effect was noted with all three antigens, it was more pronounced in the trials using B. abortus and BSA. This finding is discussed in terms of describing the importance of the GH as a source of antibodies to optically applied antigens, and its importance as a route of circulating antibody egress. Furthermore, the feasibility of using the antibody response in tears to a test antigen is discussed as a means of measuring the immune status of a functioning GH.

Animals↗
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Persistence of commercial modified live reovirus vaccines in chicks.

Four modified live reovirus vaccines were compared with a field isolate (81-176) of reovirus for safety in 1-day-old and 1-wk-old specific-pathogen-free chicks. At 1, 3, 5, and 7 wks after vaccination, blood, cloacal swabs, and hock tendon samples were collected and assayed for residual virus. Tendon samples were also examined microscopically and scored for histological changes. Vaccine efficacy was monitored by challenging chicks 7 wks postvaccination via the footpad with the 81-176 isolate. Serum samples were collected throughout the trials and assayed for reovirus antibodies using an enzyme-linked immunosorbent assay. In chicks vaccinated at 1 day of age, three of the four vaccine viruses were consistently recovered from the hock tendon tissues. Post-challenge virus recoveries were similarly positive for the same vaccine viruses. Histological lesion scores of the tendons paralleled the degree of virus recovery. In the chicks vaccinated at 1 wk old, none of the vaccine viruses were recovered, nor were tendon lesion scores substantially elevated. Following challenge, however, virus was recovered from all vaccinated groups.

Age Factors↗
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Effect of avian reoviruses on lymphoid organ weights and antibody response in chickens.

Several avian reoviruses were screened to determine their effects on the immune system by inoculating them subcutaneously (SQ) into day-old chicks. For comparison, infectious bursal disease virus (IBDV) was similarly evaluated. The response of the immune system was measured functionally by the hemagglutination-inhibition (HI) response to Newcastle disease virus (NDV) and structurally by changes in the organ-to-body-weight ratios of the bursa of Fabricius, thymus, and spleen. When inoculated SQ, most of the reoviruses caused transient alterations in lymphoid organ weights, decreasing the bursa weight and increasing the spleen weight. Of those reoviruses tested, only one--a commercial vaccine based on the isolate S-1133--demonstrated the ability to interfere significantly with NDV-HI responses, although several had numerically lower titers. Two of the isolates were also evaluated by oral inoculation. Giving the viruses orally did not cause any alterations in organ weights; however, both isolates depressed the HI response of chicks to NDV. Compared with reoviruses, IBDV significantly depressed NDV-HI titers. The structural responses to IBDV differed, however: IBDV significantly depressed bursa weights for all 3 weeks of the test period without affecting spleen weights. Some of the reovirus isolates inoculated SQ were lethal for day-old chicks. This, and their ability to alter the lymphoid-to-body-weight ratios of the spleen and bursa, could be considered valid criteria by which to study the pathogenesis of these agents.

Animals↗
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A comparison between the effect of an avian reovirus and infectious bursal disease virus on selected aspects of the immune system of the chicken.

Reovirus 81-176 was inoculated subcutaneously into day-old specific-pathogen-free leghorns and evaluated for its effects on the immune system over a 3-week period. Structural criteria included organ weights of the bursa of Fabricius (BF) and spleen (SP), scoring of histological lesions in the BF, SP, and thymus, and hematological analyses of the circulating leukocytes. Alterations in the functional capacity of the immune system were measured using the graft-versus-host reaction, the response of peripheral blood lymphocytes (PBLs) to mitogens, the ability of circulating monocytes to phagocytize latex beads, and the serological responses to Newcastle disease virus, sheep red blood cells, and Brucella abortus antigens. For comparison, infectious bursal disease virus (IBDV) was similarly evaluated by most of the same tests. Structurally, reovirus 81-176 altered BF and SP organ weights, the total numbers of white blood cells in circulation, and the degree of follicular atrophy in the BF. Functionally, reovirus inoculation reduced both the response of PBLs to the phytohemagglutinin-P stimulation and monocyte uptake of latex beads. According to the protocols used here, no significant alteration in B-cell function could be detected in reovirus-infected chicks. With the exception of leukocyte hematology, IBDV-infected chicks had significantly altered responses in all tests used. By way of comparison, the effects of IBDV were more persistent and pronounced than were those seen with reovirus. The graft-versus-host reaction indicated an elevated and/or uninhibited response of T-cells in the blood of IBDV-infected chicks.

Animals↗
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Role of route of exposure, age, sex, and type of chicken on the pathogenicity of avian reovirus strain 81-176.

Chickens were evaluated by age, sex, and type for susceptibility to reovirus strain 81-176 inoculated subcutaneously. Chicks were most susceptible to the lethal effects of reovirus infection at hatching, after which resistance increased rapidly. By 1 week of age, mortality was negligible, but chicks were still susceptible to the less lethal effects of the virus. Mortality rates of males and females were equal. Leghorn and broiler-type chicks did not differ appreciably in their response to viral inoculation. An effort was made to find a more "natural" means of exposure to reovirus than parenteral inoculation. Neither oral nor aerosol exposure was as effective as subcutaneous inoculation. Attempts to transmit reovirus to susceptible hatching chicks, starting when they were in ovo (19 days of incubation), also failed. Decreased weight gain proved to be a valid criterion for judging reovirus infection. Reovirus infection lowered the mean values of body weights, and the standard deviations were substantially greater, indicating an unevenness in size of the affected chickens.

Aerosols↗
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The 1978 epornitic of avian cholera on the Chesapeake Bay.

In an outbreak of avian cholera (Pasteurella multocida infection) in wildfowl on and around Chesapeake Bay during March and April of 1978, 31,295 carcasses were retrieved from Maryland and Virginia. Although other birds were involved, mortality was heavy among diving ducks (90% of the total), especially oldsquaw ducks (80% of the total). This is the second outbreak involving primarily diving ducks to be reported from this area of the Atlantic Flyway. It mimics in many respects the epornitic that occurred in 1970. Although mortality was heavy then, this occurrence appears much more severe and could be the largest recorded outbreak of avian cholera in North America.

Animals↗
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Observations on the pathogenicity of Alcaligenes faecalis in chickens.

A series of trials was conducted in which specific-pathogen-free (SPF) leghorn chicks were exposed to various isolates of Alcaligenes faecalis. Chicks were inoculated with A. faecalis alone or in combination with Newcastle disease/infectious bronchitis (Nc/Br) vaccine, laryngotracheitis vaccine, infectious bursal disease virus, or Mycoplasma gallisepticum. The response was evaluated by morbidity, mortality, airsacculitis, reisolation of A. faecalis, and histopathological lesions of tracheas. Although A. faecalis was recovered up to 42 days postinoculation in some cases, no clinical signs were directly attributed to simple A. faecalis infection. None of the other agents significantly increased the severity of A. faecalis signs or lesions, except that A. faecalis-infected chicks that were given Nc/Br vaccine had prolonged microscopic tracheal lesions. In another trial, the effects of A. faecalis in young SPF leghorns, non-SPF broilers, and turkeys were compared. Broiler-type chicks were more susceptible than leghorns and less susceptible than poults. Consequently, the use of leghorns as a model for studying this infection is questioned.

Alcaligenes↗