PubMed Health⌕ Search

Biomedical subjects

D H Percy

Publications and source records attributed to D H Percy.

At least 37 records · Page 2Linked to original sources
PubMed1992

Engraftment of severe combined immune deficient/beige mice with bovine foetal lymphoid tissues.

To develop a model of bovine thymus and lymph node growth in vivo, we have implanted bovine foetal tissues (16-23 weeks gestation) under the renal capsule of severe combined immune deficient (SCID)/beige (BG) mice and assayed for graft growth and characteristics 2-18 weeks after engraftment. Bovine foetal thymus and lymph node grew considerably following engraftment of SCID/BG mice. Growth was optimal if bovine foetal tissues were used before gestation Week 17. Bovine-mouse chimerism was confirmed using glucose phosphate isomerase analysis. Bovine thymus grew during the entire 18 weeks of study. Growth of bovine lymph node was initially rapid, reaching a maximum at 2 weeks after transplantation followed by a progressive decrease in size. Transplanted bovine lymph node and thymus were morphologically similar to age-matched bovine foetal tissue for a limited time period. Fibrosis, degeneration and depletion of lymphocytes were evident 6 weeks after engraftment; changes were more severe in lymph node than in thymus whereas increases in lymphocytes, lymphopoiesis and follicle formation were evident in age-matched bovine foetal tissue. Despite growth and morphological similarities of the transplanted tissue, blood counts suggested there was no peripheralization of bovine leucocytes. Bovine immunoglobulins (IgG1 and IgG2) were detected in serum of some SCID/BG chimeric mice for a limited time. The appearance of bovine immunoglobulins at 2 weeks in SCID/BG chimeric mice depended on the age of the foetal donor (> 18 weeks) and coincided with the appearance of morphologically mature lymphocytes in the donor foetus lymph nodes. The ability to produce bovine immunoglobulins decreased 8 weeks after engraftment, coinciding with the depletion of lymphocytes in the engrafted lymph node. Lymphocyte depletion and loss of function of engrafted tissues appear the result of a lack of lymphoid progenitors normally derived from hematopoietic stem cells in the bone marrow.

Animals↗
PubMed1991

A comparison of the sensitivity and specificity of sialodacryoadenitis virus, Parker's rat coronavirus, and mouse hepatitis virus-infected cells as a source of antigen for the detection of antibody to rat coronaviruses.

Sialodacryoadenitis virus (SDAV) and Parker's rat coronavirus (PRC) are two recognized viral strains which cause spontaneous disease in the laboratory rat. Currently there is no recognized practical procedure which will accurately differentiate infections with these strains. Using SDAV- and PRC-infected L-2 cells as the source of antigen, and sera from rats collected post inoculation with either of these viral strains, the indirect fluorescent antibody (IFA) procedure was used to determine whether antibody titers could be used to differentiate infections from the homologous and heterologous virus. There was no detectable difference in the sensitivity or specificity of these systems in detecting antibody to the homologous or heterologous virus. Thus there was no evidence that SDAV- and PRC-infected cells would serve to differentiate antibody to the homologous virus using the IFA technique. In addition, antibody titers were similar when mouse hepatitis virus (MHV)-infected cells were used as the source of antigen for the IFA technique. However, using MHV or SDAV-infected cells as the source of antigen, there was a significant difference in antibody titers to the homologous virus detected using the immunoenzyme technique.

Animals↗
PubMed1991

Lack of effects of viral sialoadenitis and depletion of epidermal growth factor on initiation of hepatic carcinogenesis in the rat.

Sialodacryoadenitis (SDA) is a commonly-encountered coronaviral infection in laboratory rats that causes acute destruction of submandibular salivary glands. SDA results in depletion of salivary epidermal growth factor (EGF) and may thereby affect EGF-dependent cell growth processes. The purpose of this study was to determine the effects of SDA virus (SDAV) infection on the growth factor-dependent stages of experimental liver carcinogenesis. Rats were injected ip with the carcinogen diethylnitrosamine (DENA) at 1, 2, or 3 weeks following inoculation with SDAV. Uninfected control rats were treated only with DENA. The salivary glands of SDAV-inoculated and control rats were stained using the immunoperoxidase method for the detection of EGF. Residual submandibular salivary gland lesions and focal depletion of EGF were still evident in affected submandibular glands for up to 42 days after SDAV infection. Serum EGF concentrations measured at 9, 28, and 42 days following SDAV inoculation were reduced, but were not significantly different in comparison with non-inoculated, DENA-treated control rats. Initiated hepatocytes were detected 21 days after DENA treatment in formalin-fixed sections by an immunoperoxidase stain for the P isoenzyme of the enzyme glutathione S-transferase (GST-P). There was no significant difference in the number of foci of GST-P positive cells in a comparison of initiated cells in SDAV-inoculated and non-inoculated rats. Based on this model, concurrent infection with SDAV does not appear to have any significant effects on the initial stages of chemical hepatocarcinogenesis in the rat.

Animals↗
PubMed1991

Coronavirus infection in the laboratory rat: immunization trials using attenuated virus replicated in L-2 cells.

Sixty-nine specific pathogen-free male Wistar rats approximately eight weeks of age were used to evaluate the efficacy of an attentuated strain of sialodacryoadenitis (SDA) virus in providing protection against infection on subsequent challenge with virulent SDA virus. Fifty-four animals were inoculated intranasally with approximately 10(3.5) median cell culture infectious doses of the 25th passage of SDA virus in L-2 cells. Randomly-selected vaccinated animals were killed in order to evaluate the safety and efficacy of attenuated virus by histopathological examination of the salivary glands, lacrimal glands, and lower respiratory tract, and titration of sera for antibody to SDA virus. At three months and six months postvaccination (pv), animals were selected at random and challenged with virulent SDA virus. Seronegative, age-matched animals were also challenged, and served as controls. In animals examined at six to ten days pv, lesions were absent in submandibular and parotid salivary glands and lacrimal glands, but transient lesions were present in major airways of the lower respiratory tract. In a comparison of the incidence and extent of lesions, and antibody titers in challenged vaccinates and seronegative controls, lesions were minimal or absent in vaccinates compared to challenged naive rats, particularly in animals inoculated at three months pv. In addition, antibody titers in challenged vaccinates were much higher than were postinoculation titers in inoculated controls. In a comparison of lesions in salivary and lacrimal glands in vaccinated and control animals challenged at six months pv, there was a significant reduction in the number of animals without lesions in the vaccinated group (p = less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Experimental sialodacryoadenitis virus infection in severe combined immunodeficient mice.

Mice with a severe combined immunodeficiency in B and T lymphocytes and natural killer cells (SCID-beige) were inoculated intranasally with sialodacryoadenitis (SDA) virus, a coronavirus of rats. Animals were killed at designated intervals and tissues were examined for evidence of viral infection by light microscopy and immunofluorescence microscopy. Based on these criteria, there was no evidence that these immunodeficient mice were susceptible to infection with SDA virus.

Animals↗
PubMed1991

Use of leuprolide to treat endometriosis in a rhesus macaque.

Endometriosis was diagnosed in an aged dysmenorrheic rhesus monkey (Macaca mulatta) after biopsy of a 7 cm abdominal mass which could not be completely resected due to extensive adhesions. A 6-month course of treatment with leuprolide, a gonadotropin-releasing hormone agonist, resulted in cessation of menstrual cycles and marked clinical improvement. Dysmenorrhea and hypovolemic shock occurred 2 months after therapy was completed. Despite supportive treatment and resumption of leuprolide, the primate's clinical deterioration and abdominal mass enlargement necessitated euthanasia. To our knowledge, this is the first report of a case of endometriosis in a rhesus macaque treated with a gonadotropin-releasing hormone agonist. Although prolonged leuprolide therapy was clinically effective, its cost and the difficulty in early diagnosis of endometriosis may limit its use in nonhuman primate medicine.

Animals↗
PubMed1990

Characteristics of Parker's rat coronavirus (PRC) replicated in L-2 cells.

Parker's rat coronavirus (PRC) is a naturally-occurring viral infection of the laboratory rat. On the first passage, ATCC strain 8190 of PRC replicated in L-2 cells. Using the tenth passage of PRC in L-2 cells, the characteristics of the virus were compared with previous studies of sialodacryoadenitis virus (SDAV) replicated in L-2 cells. Based on light and immunofluorescence microscopic examination of control and inoculated cell cultures, PRC-associated CPE was frequently confined primarily to individual cells, and there were relatively few syncytial giant cells. Maximum titers were recovered at 36 h post inoculation (pi). Infectious virus was demonstrated at pH values ranging from 6.0 to 9.0 and a pH of 7.5 was determined to produce the highest titers of PRC. The optimum temperature for viral replication was 33 degrees C. Up to 15 passages of PRC in L-929 cells failed to produce detectable virus. However, after adaptation in L-2 cells (20th passage), PRC replicated to high titers in L-929 cells. Previously, in vitro studies of rat coronaviruses have been hampered by the lack of an identified continuous cell line to replicate these viruses in the laboratory. L-2 cells represent a readily-available continuous cell line that can support the replication of relatively high titers of PRC.

Animals↗
PubMed1990

Duration of protection from reinfection following exposure to sialodacryoadenitis virus in Wistar rats.

Wistar rats [Cr1:(WI)BR] were inoculated intranasally with approximately 10(3) median mouse lethal infective doses of sialodacryoadenitis (SDA) virus. Animals were subsequently selected at random, removed to a separate isolation room, and reinfected with SDA virus at 3, 6, 9, 12 or 15 months. Pre- and postinoculation serum samples were collected from all animals during the course of the study and evaluated for antibody titers to SDA virus. All experimental, control and sentinel animals, following inoculation with SDA virus, were necropsied and examined for lesions consistent with SDA. Salivary gland lesions were minimal to absent in rats reinfected with SDA virus for up to 12 to 15 months after the initial exposure and minimal to moderate in the respiratory tract at 12 or 15 months. SDA-associated lesions were extensive in age matched control animals examined at each time period of reinfection with SDA virus. Thus, prior exposure to SDA virus did protect against the development of typical salivary gland lesions for up to 15 months. Recovered animals were evaluated for their ability to transmit the virus following reinfection. Rats reinfected at 6 or 9 months were infectious to their naive cage mates. The results indicate that reinfection with homologous rat coronavirus can occur as early as 6 months after the initial infection, and such rats can transmit the infection to contact controls.

Animals↗
PubMed1990

Experimental Parker's coronavirus infection in Wistar rats.

Specific Pathogen Free (SPF) male Wistar rats were inoculated intranasally with Parker's rat coronavirus (PRC), then killed at various intervals post-inoculation (pi). PRC inoculated rats had transient respiratory signs. Intermandibular swelling was evident in some rats at 6-8 days pi. During the acute stages of the disease, inflammatory lesions were present in the respiratory tract and in the salivary and lacrimal glands. Regenerative lesions were observed in the salivary and lacrimal glands at 2 weeks pi. Inoculated rats seroconverted at 8-14 days pi, and significant coronaviral antibody titers were present in inoculated rats examined at 21 days pi with PRC. Changes in the respiratory tract and salivary and lacrimal glands were identical in incidence, distribution and nature to those observed in sialodacryoadenitis (SDA) virus inoculated Wistar rats. Thus, in the absence of viral isolation and characterization, "rat coronavirus infection" is a more appropriate term than either PRC infection or sialodacryoadenitis (SDA).

Animals↗
PubMed1990

Long-term feeding of casein or soy protein with or without cholesterol in Mongolian gerbils. I. Morphologic effects.

This study was designed to determine whether male Mongolian gerbils (Meriones unguiculatus) develop atherosclerosis (AS) during long-term feeding of diets similar to those consumed by humans. Gerbils were fed diets containing 16% casein (C) or soy (S) protein +/- 0.1% cholesterol (CH) for 15 months. The energy contribution from protein, fat and carbohydrate was similar to the energy distribution reported for the average North American (NA) diet and the level of added dietary CH resembled the average NA intake. At mo 0, 3, 6, 9, 12 and 15, animals were killed and tissue sections were prepared for histologic examination. Microscopic observations of cardiovascular tissues did not reveal any evidence of AS in any of the diet groups. Liver fatty infiltration (FI) was evident in the C+CH and C groups at mo 3 and 9, respectively, and continued to occur at all subsequent sampling times. Livers from gerbils fed S+CH also began to exhibit FI at mo 9, while livers from S-fed gerbils did not show any significant morphologic changes. Biochemical liver total lipid results supported the histological liver findings. Other tissues examined did not reveal any morphological changes related to diet. The gerbil may be a useful animal model to study mechanisms which inhibit AS development.

Animals↗
PubMed1989

Sequential changes in the harderian and exorbital lacrimal glands in Wistar rats infected with sialodacryoadenitis virus.

A sequential light and electron microscopic study of the exorbital and Harderian lacrimal glands was done on 2.5- to 15-month-old Wistar rats exposed to sialodacryoadenitis (SDA) virus. Typical coronaviral particles were readily demonstrated in cytoplasmic vesicles of Harderian and exorbital glands examined at 6 days post-inoculation. Lesions were seen in a relatively high percentage of lacrimal glands in infected animals of all ages, with no obvious age-related variations in the incidence and extent of changes. Lesions frequently persisted for a longer interval post-exposure in lacrimal glands than in salivary glands. The persistence of lesions commonly seen in Harderian glands was attributed, at least in part, to the cytotoxic effects of porphyrin-containing secretions released during the acute necrotizing stages of the disease. The persistence of lesions in some lacrimal glands indicates that they are useful tissues for microscopic examination for the retrospective provisional diagnosis of SDA. Persistent lesions also indicate that normal functions of these glands may be compromised for up to several weeks following outbreaks of SDA.

Age Factors↗
PubMed1988

Morphometric evaluation of hepatocellular proliferative lesions in the rat liver.

Classification of rat hepatocellular proliferative lesions can vary between pathologists as the many qualitative histologic criteria have not been satisfactorily evaluated and ranked for prognostic value. Computer-assisted morphometry offers an objective method to evaluate certain cellular features. The Solt-Farber resistant hepatocyte model was used in this study to produce populations of rats with a full range of hepatocellular proliferative lesions. Cellular features within the lesions were then measured morphometrically and the data were analyzed by animal age and by subjective lesion diagnosis. The nuclear/cytoplasmic ratio followed by the cell area and nuclear area were found to be the most important parameters for separating microscopic foci and islands of cellular alteration, an early hyperplastic lesion, from other hepatocellular proliferative lesions. The coefficient of variation, as a relative measure of heterogeneity, increased in a linear manner for cell, nuclear and nucleolar areas as the animals aged and was significantly higher for cell and nuclear area in hepatocellular carcinoma compared to other hepatocellular proliferative lesions. Hepatocyte nodules (representing primarily late hyperplastic lesions) and persistent hepatocyte nodules (lesions with similarities to hepatocellular adenoma) could not be satisfactorily separated within the limits of this study. As these borderline lesions show a continuum of cytologic change, other features, such as architectural change, are necessary to satisfactorily classify them on a subjective basis. An alternative approach is to use discriminant functions derived from morphometric studies.

Animals↗
PubMed1988

Depletion of salivary gland epidermal growth factor by sialodacryoadenitis virus infection in the Wistar rat.

Male and female Wistar rats 2 to 15 months of age were inoculated intranasally with sialoda-cryoadenitis (SDA) virus and killed at 8 to 21 days post-inoculation (PI). Submandibular glands were evaluated by light and electron microscopy, and levels of salivary gland epidermal growth factor (EGF) were quantitated by cytochemistry and competitive radioreceptor assay. Apical granules in the epithelial cells of the granular convoluted tubules (GCT) were selectively depleted during the acute and convalescent stages of the disease. In addition, levels of immunoreactive EGF were reduced in affected submandibular glands, especially at 8 to 14 days PI with SDA virus, but some evidence of EGF depletion was seen at up to 3 weeks PI. A corresponding transient depletion of EGF receptor reactive salivary EGF was seen between 1 and 3 weeks after experimental SDA infection. These studies suggest that a clinical (or subclinical) infection with SDA virus could have significant effects on experimental studies on EGF-dependent functions, including reproductive physiology and carcinogenesis.

Animals↗
PubMed1988

Experimental sialodacryoadenitis virus infection in athymic CD-1 mice.

The purpose of the study was to investigate the susceptibility of nude mice to sialodacryoadenitis virus. Young adult male CD-1 nude mice were inoculated intranasally with virus, killed at 2, 4, 6, 8, 10 and 20 days postinoculation and examined for virus-induced lesions in tissues including respiratory tract. Inoculated and control mice were examined by virus isolation and serology. In a companion study, male Wistar rats were inoculated intranasally with the same inoculum, and examined by histopathology, immunofluorescence microscopy and serology. In virus-inoculated mice, lesions were minimal in the lower respiratory tract, and were absent in other tissues. Virus was isolated from the lower respiratory tract in animals sampled at six or eight days postinoculation. Antiviral antibody was not detected in sera from inoculated and control mice. Virus-associated lesions and antibodies were readily detected in rats following inoculation. Based on this study, there is no evidence that inadvertent exposure to sialodacryoadenitis virus should pose a threat to CD-1 nude mice, and their susceptibility to the disease appears to be similar to that reported in euthymic CD-1 mice.

Animals↗
PubMed1988

Pharmacokinetics of tetracycline in the domestic rabbit following intravenous or oral administration.

Tetracycline hydrochloride was administered to domestic rabbits using a single bolus by the intravenous and oral routes. Pharmacokinetic parameters were determined for intravenous (10 mg/kg) and oral (150 mg/kg) administration. The effect of fasting for 12 h on the drug elimination kinetics after oral administration was evaluated. Tetracycline was added to the drinking water at 800 mg/L or 1600 mg/L. Drug and water intake and serum levels were monitored. Mean serum pharmacokinetic parameters following intravenous administration were; 0 intercept beta curve B (microgram/mL) = 7.5, rate of elimination from body -b (min-1) = 0.0058, half life elimination from body -t 1/2 b (min) = 120.0, wt(kg) = 3.2 determined using combined male and female data. Mean serum pharmacokinetic parameters after oral administration (single bolus) were -B (microgram/mL) = 1.54 (full stomach) and 2.71 (empty stomach), b(min-1) = 0.0037 (full stomach) and 0.0035 (empty stomach), t 1/2 b (min) = 190.3 (full stomach) and 216.2 (empty stomach). Administration of tetracycline in the drinking water produced very low to nondetectable levels of drug in the serum, even at high dosage, and the 1600 mg/L drug concentration was accompanied by a significant drop in water intake. Thus, it is evident that concentrations of tetracycline of up to 1600 mg/L drinking water will not produce levels of antibiotic consistently detectable in the serum.

Administration, Oral↗